Between 1986 and 1989 the Social Insurance Institution of Finland sent 373 people with psoriasis to the Canary Islands for four weeks of sunbathing. They went in nine groups of 33 to 45, in March, April, or November, and each group traveled with a Finnish dermatologist, two or three nurses, and a sports-and-leisure leader. Around noon the patients lay in the sun on a schedule set by their skin type, starting with half an hour or an hour and working up to six hours a day. Most had had psoriasis for more than ten years, and 76 percent had already been treated with PUVA, a hospital treatment that pairs a light-sensitizing pill with an ultraviolet lamp. Alcohol abuse took 6 percent of them off the schedule for a while, and in one group most of the patients caught a cold in the first days. 1
After four weeks the median score on the team's psoriasis scale, which ran from 0 to 60, had fallen from 4.5 to 0.2. Eighty-four percent of the patients had improved by at least three quarters, and 22 percent were clear. Six months later the psoriasis had come fully back in 49 percent of the 258 patients the team could follow, and 271 of 361 who returned monthly questionnaires had started another treatment, a median of 80 days after the trip. 1
In the studies that sent people with psoriasis or atopic eczema into real sun for two to four weeks, most of them improved, and the improvement faded over the following months. Almost all of those studies were run by the health services, patient associations, or clinics that sent the patients, and we found none that compared the patients' skin with that of people who stayed home. Patients from Denmark treated in the sun at the Dead Sea later had more skin cancer than was expected for people in Denmark of their age and sex. Some people with psoriasis, eczema, or rosacea get worse in the sun, and for acne we found no trial of sunlight at all.
This page covers how light became a treatment for skin disease, the state-paid sun trips for psoriasis and the skin cancer that followed, sun taken with plant drugs, what sunlight does to vitiligo and eczema, the little that is known about acne and rosacea, and why fewer patients are sent south. Each study is named as real sun, a lamp, a pill or cream taken with sun, cells in a dish, a registry, or a survey.
Key facts
- In 373 Finnish psoriasis patients given four weeks of Canary Islands sun, the median severity score fell from 4.5 to 0.2 on a 60-point scale, and six months later the psoriasis had fully returned in 49 percent of the 258 followed. 1
- Measured at the Dead Sea from 1996 to 2019, sunlight near 300 nanometers, the most burning band, was 21 to 27 percent weaker than 690 meters higher in Beer Sheva, and the band that clears psoriasis was 11 to 15 percent weaker. 2
- Of 1,738 people from Denmark sent to the Dead Sea for psoriasis from 1972 to 1993, basal cell carcinoma later ran at 4.2 times the expected rate and squamous cell carcinoma at 10.7 times. 3
- Of 869 people referred for light testing in Manchester from 2015 to 2019, 120 (14 percent) had eczema made worse by light. 4
- Among 51,337 American nurses, those who had had at least one blistering sunburn were diagnosed with vitiligo about twice as often as those who had not. 5
The first light cures treated tuberculosis, with a carbon-arc lamp in Copenhagen and sunshine in the Alps
"I suffered from anaemia and tiredness, and since I lived in a house facing the north, I began to believe that I might be helped if I received more sun," Niels Finsen wrote of the illness that started his work on light. In November 1895, in Copenhagen, he began treating his first patient with lupus vulgaris, a tuberculosis of the skin that ate into the nose, eyelids, lips, and cheeks. Lupus vulgaris is a different disease from lupus erythematosus, the autoimmune disease most people now mean by lupus, whose rash, Britain's National Health Service (NHS) says, usually comes on after being in the sun. 6; 7; 8
In the words of the 1903 Nobel presentation speech, "Sunlight, or more frequently the light from a powerful electric-arc lamp" was passed through lenses into a beam with the heat filtered out, and the beam was held for an hour on a small patch of skin pressed bloodless. The lamps were carbon arcs, later known as Finsen lamps, and his lenses concentrated the light about 15 times onto a patch about 2 centimeters across. 7; 9; 10
In 1902 Finsen reported 804 patients to a tuberculosis meeting in Berlin. Of these, 412 were cured and 192 nearly cured. The Nobel speech put the cure rate at 50 percent and the failures at about 5 percent. A 2026 history of ultraviolet therapy gives 80 percent cured, a figure that is not in his table. 10; 7; 11
On 10 December 1903, while the prize was presented in Stockholm, Finsen sat in his wheelchair at home and received congratulations from his staff. He had Pick's disease, a thickening of the membranes around the heart, liver, and spleen, and he died on 24 September 1904. 6
In 1903 the Swiss physician Auguste Rollier began giving sun baths at a clinic in Leysin, in the Alps, for tuberculosis of the bones, joints, and glands, which was then called surgical tuberculosis. Patients were wheeled out in their beds in loincloths, each under a white sheet. On the first day the sheet was raised just above the ankles and the feet were left in the sun for five minutes, three times. It took about fifteen days to bare the whole body, and then two to three hours a day was the summer dose, given between 6 and 9 in the morning. 9
Above 18 degrees Celsius Rollier called it "a hot-air bath" and not a sun bath. "A very current mistake consists in thinking that the sun bath is all the more efficacious if prolonged or taken when the sun is at its hottest," he wrote. Over forty years he ran 36 clinics with more than 1,000 beds, while many physicians in Switzerland and elsewhere tried sun on tuberculosis of the lungs and gave it up as too hazardous. Antibiotics replaced sun and ultraviolet lamps for tuberculosis in the 1950s. 9; 12
Clinics moved the cure indoors, under lamps that give out the band of sunlight that clears psoriasis
In 1925 William Goeckerman of the Mayo Clinic reported a hospital treatment for psoriasis. Crude coal tar stayed on the plaques for 24 hours and came off with olive oil, and then came ultraviolet from a quartz lamp and a soap-and-water or "oatmeal and soda bath", every day. "If the therapist is thoroughly acquainted with the effectiveness of his lamp and handles it deftly," he wrote, "it should be possible to remove all patches of psoriasis, in practically all cases, in from three to four weeks." 13
More than 3,500 years ago, according to a history of phototherapy, healers in Egypt and India gave plant extracts or seeds by mouth and then sunlight for "leucoderma", white patches of skin. In 1947 the Egyptian dermatologist A. M. El-Mofty isolated psoralens, the light-sensitizing chemicals, from the plant Ammi majus and used them with sunlight on vitiligo. In 1974 John Parrish, Thomas Fitzpatrick, and two colleagues reported the indoor version for psoriasis, a methoxsalen pill followed by long-wave ultraviolet, UVA, from a lamp. The combination is called PUVA. 14; 11; 15
In 1981 Parrish and K. F. Jaenicke set out to find which wavelengths do the clearing. They used a monochromator, an instrument that picks out one narrow band of light at a time, to give psoriasis plaques daily doses at seven wavelengths from 254 to 313 nanometers. At 254, 280, and 290 nanometers the light reddened the skin but did not clear the plaques "even at 10 to 50 times the minimal erythema dose", the smallest dose that leaves skin just visibly red a day later. From 296 to 313 nanometers, the curve for clearing psoriasis followed the curve for reddening skin. 16
In 1988 van Weelden and colleagues compared a new Philips fluorescent tube, the TL-01, which gives out a narrow peak at 311 to 312 nanometers, with the older broadband tube in 10 patients with psoriasis. The new tube worked better in 9 of the 10, and hairless mice under it took longer to grow tumours. Narrowband ultraviolet B (UVB), as the treatment is called, reached the market in the 1990s and replaced the older broadband lamps. 17; 11
Nordic health services paid for sun trips that cleared most psoriasis within a month, and half the patients had fully relapsed by six months
A 1968 report described "Travelling to the Canary Islands for psoriasis", and a 1972 one described climate therapy for Swedish patients on the island of Hvar, in Yugoslavia. Norway's public health service began paying for three- to four-week trips in the 1970s, first to Yugoslavia and later to Lanzarote and Gran Canaria, as an alternative to the same weeks in hospital with dithranol or coal tar. The Norwegian Association of Psoriasis and Eczema Patients lobbied for the trips, and they got their own item in the state budget. In 2011 an Oslo team put the number of Norwegian psoriasis patients selected for them at about 500 a year. 1; 18; 19
The Finnish trips of 1986 to 1989 took patients of working age whose psoriasis had improved with sun or lamps before, and left out anyone of skin type I, who always burns. The team built its own severity scale, because the standard Psoriasis Area and Severity Index (PASI) missed changes in patients with less than a tenth of their skin affected, a third of the group. Skin type made no difference to the result, and 11 of the 373 patients had a blistering sunburn. Fourteen percent also used dithranol, an older psoriasis ointment, for short spells. 1
In the 129 Finnish patients with active arthritis, the team's joint score fell from 6 to 2 during the month, and in the 55 examined six months later it stood at 8, no better than before. A Norwegian group of 254 adults sent for three weeks scored their own psoriasis, and the score fell from 8.6 to 1.6 and was back at 6.4 three months later, still below where it began. The American psoriasis guideline of 2019 recommends climate therapy and notes that its benefit seems "to wane after a few months" and that "there have been no formal studies on the remission duration". 1; 20; 21
In a second study the Finnish team followed 46 patients for a year before and a year after a four-week trip. The trip cost 12,289 Finnish marks per patient, about 1,750 pounds at 1989 rates, and nearly 60 percent of it went on flights and half-board. Spending on psoriasis drugs fell 22 percent in the year after, a change too variable between patients to be sure of, and the trips saved money only for those with severe psoriasis who would otherwise have needed expensive drugs or a hospital ward. 22
Sun changed immune cells in psoriatic skin within two days, and vitamin D pills did not change psoriasis
One March, the Section for Climate Therapy at Oslo University Hospital flew 20 Norwegian patients with psoriasis to Gran Canaria and took skin biopsies before the first day of sun, on day 2, and on day 16. On the first day each patient had an hour and a half of sun, "equally divided between the front and back sides", an estimated 5.1 standard erythema doses, the fixed unit of sunburning ultraviolet that meters record. Seventy percent reported red skin after that first day, and by day 16 none had visible redness. Over 15 days the dose added up to an estimated 166 standard erythema doses. The section and the Norwegian Psoriasis Association paid for the study. 19; 23
The patients' PASI scores fell by an average of 72.8 percent in 16 days, and all 20 improved. The dermatologist who scored them "was unaware of the duration of sun exposure" each patient had had, the only blinding we found in any of the trip studies. In the blood, the T cells that travel to the skin had fallen by day 2. In biopsies of the plaques, dendritic cells, immune cells that keep psoriatic inflammation going, were already lower on day 2 and clearly lower by day 16. The authors wrote that they "cannot completely rule out" that stress reduction helped, and concluded that the effect was "primarily due to sun exposure". 19; 23
A Gothenburg team set those 20 patients beside patients given two to three months of hospital UVB lamps, and psoriasis scores had fallen by about three quarters in every group. The groups came from separate studies, and nobody was assigned to sun or lamp by chance. 24
A Finnish team had measured the skin on the Canaries in the autumn of 1989, sampling urocanic acid, a molecule in the outer skin that changes shape when ultraviolet reaches it, in 27 patients. The molecule changed after the first half hour to hour of sun, and its levels seemed unrelated to how well each patient's psoriasis cleared. The team wanted unexposed skin to compare with and had none, because "the patients sunbathed undressedly." 25
In Tromsø, Norway, 122 adults with plaque psoriasis and low vitamin D took vitamin D or a dummy pill for four months, over two winters from 2017 to 2019. Blood vitamin D ended at 29.7 nanograms per milliliter in the vitamin D group against 12.0 in the dummy-pill group. The change in PASI differed between the groups by 0.11 points on a scale that runs to 72. The 95 percent confidence interval, the range in which the true difference probably lies, ran from 0.23 points one way to 0.45 the other. The authors noted that the patients' psoriasis was mild at the start, a mean PASI of 3.1, and that vitamin D rose less than they had expected. 26
Dead Sea sunlight is about a quarter weaker in the burning band than Beer Sheva's, and most of its results come from the clinics that treat the patients
The shores of the Dead Sea, about 400 meters below sea level, are the lowest land on earth. Israeli doctors first reported on skin disease at the hot springs of Zohar, beside the lake, in 1959. In 1985 D. J. Abels and J. Kattan-Byron described 110 psoriasis patients treated with sun there, 85.5 percent with "complete clearing or excellent improvement", and called the light "a naturally filtered ultraviolet spectrum of sunlight". 2; 27
From the mid-1990s a team led by Avraham Kudish of Ben-Gurion University ran identical ultraviolet meters at Neve Zohar, on the western shore 375 meters below sea level, and in Beer Sheva, 315 meters above it. From 1996 to 2019 the Dead Sea got 6.6 to 11.7 percent less UVB than Beer Sheva, depending on the month. Measured wavelength by wavelength with a spectroradiometer, sunlight near 300 nanometers, where burning peaks, was 21 to 27 percent weaker at the Dead Sea, and near 312 nanometers, the band that clears psoriasis, 11 to 15 percent weaker. The American psoriasis guideline of 2019 gives another account, "an ever-present miasma of salt and mineral-infused moisture that is thought to diffuse and mitigate the sun's rays". 2; 21
Kudish's team found the ratio of healing to burning light worst at noon and advised sunbathing in the early morning or late afternoon, or under sunshades for 20 to 25 percent longer. Their co-author Marco Harari works at the DMZ Medical Center in Ein Bokek, where, the paper says, most psoriasis patients at the Dead Sea have been treated for 40 years. Citing earlier reports, the paper puts excellent to complete clearance after four weeks at over 85 percent, and it puts remission at more than six months "based upon our years of experience treating psoriasis at the Dead Sea". It declares no conflict of interest. 2
Clalit Health Services, Israel's largest health insurer, audited 85 of its members treated at Ein Bokek from 2003 to 2006, for 14.5 days on average. Their mean PASI fell from 17.5 to 4.4, and 43 of 78 improved by at least three quarters. Patients who took more than three hours of sun a day had 8.9 times the odds of improving by half, and the true figure could lie anywhere from about 1.5 to 54 times. The time spent in the Dead Sea water made no difference, and 83.5 percent of the patients took more than the three hours of sun a day that the guidelines advise. 28
A 43-year-old German man with psoriasis for 30 years had turned red all over after a tetanus vaccination. He stopped his drugs a week before flying to the Dead Sea, sunbathed twice a day for up to four hours, and was clear in four weeks, "leaving a tanned skin". One of the three authors of that 1995 report worked at the Ein-Bokek Clinic, which treats such patients, and the five months of remission that followed came from the patient's own report. Denmark's national guideline does not recommend salt-water baths with light over narrowband UVB alone, "since the additive effect of the salt-water baths is not documented" (our translation). 29; 30
Psoriasis patients from Denmark sent to the Dead Sea later had 4 times the expected basal cell carcinomas and 11 times the squamous cell carcinomas
In 1999 Danish researchers linked 1,738 people sent to the Dead Sea for psoriasis between 1972 and 1993 to the national cancer registry. They later developed basal cell carcinoma at 4.2 times the rate expected for people in Denmark of the same age and sex, and squamous cell carcinoma at 10.7 times, both of them cancers of the outer skin, and they had no excess of cancer in general beyond the skin. Among younger patients and at multiple sites the ratios were 10.7 and 57.2, and several basal cell carcinomas at once were particularly common in young women. The authors wrote that their design could not separate the Dead Sea from other ultraviolet, because "climatotherapy is inevitably confounded by excess UV exposure". 3
In 2003 two Dead Sea researchers wrote that skin cancer was "the only potentially serious (albeit unproven) long-term side effect of heliotherapy". They showed in 194 patients that three hours of sun a day, about half the five to six hours of the traditional schedule, worked in every month from March to November, and that the smallest cumulative dose that worked, in March and November, was 170 standard erythema doses. 31
Among 1,380 American patients first given PUVA for psoriasis in 1975 and 1976, 237 had developed 1,422 squamous cell carcinomas by 1996. Those with 337 or more treatments had 8.6 times the risk of those with fewer than 100, and the true figure could be anywhere from about 5 to 15 times. From 1991, about 15 years after their first treatment, the same patients had 5.4 times the expected rate of melanoma, 7 cases, with the true figure anywhere from about 2 to 11 times. In Tayside, Scotland, 3,867 patients given narrowband UVB, a median of 29 treatments each, showed no link with any skin cancer, and the authors warned that few had many treatments and that skin cancers are slow to appear. 32; 33; 34
About one psoriasis patient in twenty gets worse in sunlight
The Finnish trips took only patients who "had previously derived benefit from exposure to natural or artificial ultraviolet (UV) radiation", so patients whose psoriasis worsens in the sun would not have qualified. In 1992 the dermatologist A.-M. Ros put them at 5.5 percent of people with psoriasis. They more often had the palest skin type, were older, and had psoriasis on the hands. Half of them first get polymorphic light eruption, an itchy rash that follows sun, and psoriasis then grows in the rash; the other half develop psoriasis slowly after sun, with no rash first. 1; 35; 36
In 2009 Rutter, Rhodes, and colleagues described 20 patients with severely photosensitive psoriasis. Nineteen were women, their psoriasis had begun at an average age of 11, and 16 of 17 tested carried the same immune gene variant, HLA-Cw*0602. Seventeen of the 20 reacted abnormally to UVA from a lamp. When 10 of them had low doses of UVA on three days in a row, biopsies showed early psoriasis in 4, and in none of 9 psoriasis patients without light sensitivity or 11 healthy volunteers. 37
In a 2026 survey of 119 Polish adults with plaque psoriasis, 89.9 percent said their psoriasis changed with the seasons, best in summer and worst in winter. The researchers estimated each person's sun from the ultraviolet modeled for their postal code, weighted by their time outdoors and scaled to their own burn threshold, and those in the top quarter had 4.65 times the odds of improving, and the true figure could be anywhere from about 2 to 10.6. Past a certain daily dose the benefit shrank again, a turning point the authors called exploratory. The NHS lists sunlight among the triggers of psoriasis, and the British Association of Dermatologists writes that UV light helps many people and "for others, UV light can worsen psoriasis." 38; 39; 40
Where clinics have no lamps, psoralen with sunlight matched psoralen with a lamp at less than half the cost
In New Delhi, at 28 degrees north, the sun gives UVA "almost throughout the year", and dermatologists at the All India Institute of Medical Sciences tested it against their PUVA cabinet. They randomly assigned 59 adults with plaque psoriasis to methoxsalen with a UVA lamp in the hospital three times a week, or to the same drug followed two hours later by sun at home three times a week, between 11 in the morning and 3 in the afternoon, starting at 5 minutes and rising to 30. The home version is called PUVAsol. Only patients "who had a facility for sun exposure at their residence" could join. Of the 36 who finished 12 weeks, 15 of 16 responded to the lamp and 15 of 20 to the sun, a difference the trial was too small to tell from chance. 41
The lamp worked faster, cutting PASI by 44 percent at two weeks against 29 percent for the sun, and the lamp and the sun were level from week 8. Patients on the lamp made a median of 26 hospital visits and those on the sun 6, and the median total cost, counting travel and lost wages, was 62.7 US dollars against 26.8. All ten patients who dropped out of the sun group stopped coming, while the lamp group lost nine that way and four more to whole-body redness or severe burning. 41
In Montenegro, which "has plenty of sunshine days throughout the year, but does not own the Cabinet for artificial phototherapy", dermatologists followed 27 people with psoriasis who sunbathed three to four hours a day on their own two-week summer holidays in 2020. Their average PASI went from 11.3 to 7.3 and was 8.6 three months later, and none cleared completely. In Yogyakarta, where "phototherapy facilities for skin diseases are not widely available", a 2025 study timed how long the 10 a.m. sun took to redden 48 healthy volunteers with skin types III and IV, and it came to about 18 to 23 minutes, less at higher altitude. 42; 43; 44
Sunlight repigmented some vitiligo with or without plant drugs, and a blistering sunburn went with a higher risk of vitiligo
In vitiligo the immune system destroys the pigment cells in patches of skin, which turn white, and a 2025 review puts it at 1 to 2 percent of the world's population. In the winter of 1979 to 1980, a team from Ain-Shams University and the National Research Centre in Cairo gave 60 vitiligo patients aged 7 to 60, whose patches had not responded to other treatment, either a daily 100-milligram tablet of khellin, a chemical from the plant Ammi visnaga, or a dummy tablet, without patients or doctors knowing which. Forty-five minutes after the tablet every patient sat in the sun for 15 minutes between 11 and 3, when, the authors noted, the sun's long-wave ultraviolet ran at 7,500 microwatts per square centimeter. 45; 46
After four months, 23 of the 30 on khellin had some new pigment, and 5 of them had repigmented 90 to 100 percent of the treated areas. None of the 30 on the dummy tablet had any. The team estimated repigmentation from photographs taken before and after, and reported no side effects and no relapse in the following year. 46
In 1992 G. Orecchia and L. Perfetti at the University of Pavia gave 41 vitiligo patients up to 90 minutes of sun three times a week for four months. Before each session they painted the white patches on one side of the body with a 2 percent khellin solution and, in 36 of the patients, the patches on the other side with the same solution without khellin. More than half the area repigmented in 24.9 percent of the khellin patches and 22.3 percent of the dummy patches, and no patch passed three quarters. The Cairo patients had sat in the sun for 15 minutes a day, and the Pavia patients for up to 90 minutes three times a week. 47; 46
In 2020 dermatologists at Children's National Hospital in Washington described an American-born 3-year-old whose family had visited relatives in Ethiopia. A dermatologist there told his mother to paint his white patches with methoxsalen solution and put him in the sun for 5 minutes, adding a minute each time. His eyelid partly repigmented within a month, and after one session the skin was "red and tender for several days". The Washington clinic stopped the methoxsalen because it was going on an eyelid, and three months later the new pigment had gone. 48
A 32-year-old Indian flight attendant with a 15-year-old band of vitiligo could not take psoralens, to which he was allergic, and "international aviation regulations" had made it hard to carry a home UVB lamp between countries. In 2019 his dermatologist in Gurugram gave him a cream meant to let through mostly the band near 311 nanometers, and after 12 weeks of sun through the cream more than 75 percent of the patch on his back had repigmented. The paper declares no financial support, and its acknowledgements thank staff of the drug company Cadila Healthcare for supplying all of the cream and his other drugs "completely free to the patient". 49
The NHS tells people with vitiligo that "Sunburn is a severe risk", advises against home sunlamps, and offers phototherapy in hospital. 50
Among 51,337 white American nurses, 271 were diagnosed with vitiligo over follow-up that added up to 835,594 years. Those who had had at least one blistering sunburn had 2.17 times the risk, and the true figure could be anywhere from about 1.2 to 4.1 times. Women who tanned more easily also had a higher risk, 2.59 times. 5
In a postal survey of 1,307 vitiligo patients aged 50 or older and their partners, the patients had about a third of their partners' odds of melanoma and of other skin cancers. In American health records of 123,179 patients, vitiligo went with 17 percent fewer skin cancers and 31 percent fewer melanomas, except in an exploratory look at Black patients, who had about twice the squamous cell carcinomas. A 2025 meta-analysis, a study that pools the results of earlier studies, found "no consistent associations" either way. 51; 52; 45
Real sun eased eczema in small studies without comparison groups, and light makes eczema worse in some people
Atopic eczema, also called atopic dermatitis, is an itchy skin condition that is most common in young children. In January and March 2005, 23 Finnish adults with atopic eczema went to Gran Canaria for two weeks on the kind of course a Finnish patient association had run there for years. On the first day they lay in the sun for 15 or 30 minutes, without sunscreen, and added 15 minutes a day up to two hours, after which they covered up and used sunscreen. 53; 54
The median score on SCORAD, the standard eczema severity scale, fell from 34 to 9 in the January group and from 30 to 9 in March, although the March group received about twice the ultraviolet, partly because January was "unfavourably cloudy". "It is much more difficult to standardize HT than the UVB treatments given in outpatient clinics at home," the authors wrote, HT being heliotherapy. 54
At a clinic in Davos in 1991, 53 patients with atopic eczema were assigned by chance to lie naked in the sun on the clinic's roof garden at midday for an average of 19.3 hours over three weeks, or for 5.7 hours. The outcome was how well they rode an exercise bicycle. At the end, lactic acid in the blood at the same workload was 0.5 millimoles per liter lower in the sun group. 55
On the Montenegrin coast in the summer of 2021, 24 patients with eczema who had summer homes by the sea sunbathed three to four hours a day for two weeks, avoiding the strongest hours and without sunscreen, under a UV index of 6 to 9. Their average SCORAD fell 40 percent, from 25.9 to 15.1, and three months later it was still 31 percent below where it began. Two others dropped out because of "job duties and a sudden business trip". 42
In Perth, in a trial of vitamin D drops from birth, 82 babies wore ultraviolet meters made of bacterial spores, clipped at head or shoulder level, for their first three months. The 16 who had eczema by six months had received a median of 555 joules per square meter, against 998 for the 64 without it. At two and a half years, children with eczema had spent 7 minutes a day outside between 11 and 3 in their first three months, against 20, while their total time outdoors did not differ. The meters were worn from birth to three months and eczema was counted to six months, so the study could not tell whether less sun came before the rash or after it. 56; 57
At the photobiology unit in Manchester, 120 of 869 people referred for light testing from 2015 to 2019, 14 percent, had eczema made worse by light. Among the 28 whose single-wavelength tests were abnormal, UVA near 350 nanometers was the commonest trigger. The authors cite estimates that 1.4 to 16 percent of people with eczema have this form. 4
A 2025 meta-analysis of 42 studies of weather and eczema in adults rated the link between hours of sunlight and eczema severity as "uncertain", with very low certainty, and found that high humidity probably makes eczema worse. The NHS lists "heat or changes in temperature" among eczema triggers and does not list sunlight. 58; 53
No trial has tested sunlight on acne or rosacea, and the studies are surveys, case reports, and lamps
In 2005 a team led by the general practitioner Parker Magin at the University of Newcastle in Australia reviewed the evidence on diet, face-washing, and sunlight in acne and found "surprisingly little evidence" either way for any of them. In a 1996 survey at the Technical University of Munich, 139 patients were asked how the seasons affected their acne, and about a third said winter made it worse, a third summer, and a third saw no change. The Munich authors saw no reason to treat acne with ultraviolet "because of all its negative effects on the skin", while allowing that sunbathing "may be beneficial for psychologic reasons and may produce euphoric effects". 59; 60
In Delhi, 69 of 171 acne patients (40 percent) said summer made their acne worse and 11 (6 percent) said winter did. A 2023 review, two of whose nine authors work for the sunscreen maker ISDIN, wrote that sun "can temporarily improve lesions" but can leave dark and red marks after spots heal and can start flares, and it found only four studies of sunscreen in acne. We found no study that followed acne in real sun. 61; 62
In 1975 O. H. Mills and Albert Kligman reported the first American case of acne aestivalis, an acne-like eruption that came back every summer in one woman. In 1998 dermatologists in Santiago de Compostela described a 31-year-old doctor with pustules on his upper back and shoulders that appeared 48 to 72 hours after each year's first sun, for four years, set off by about 15 minutes of exposure, with "no history of common acne". Such summer eruptions have been grouped under the name actinic folliculitis. The doctor "was not willing to undergo provocation tests with ultraviolet (UV) radiation, additional histological sampling for immunohistochemical studies, or speculative treatment." 63; 64
Rosacea is a long-term redness and flushing of the face. In 2002 the US National Rosacea Society surveyed 1,066 patients, and 81 percent said sun aggravated their rosacea, 79 percent emotional stress, and 75 percent hot weather; the society's report does not say how respondents were chosen. At the Twins Days festival in Twinsburg, Ohio, dermatologists examined 275 pairs of twins in 2012 and 2013, and rosacea scores rose with lifetime ultraviolet exposure (a correlation of 0.26, where 1 is a perfect match) and with age (0.38). 65; 66; 67
In 2025 a team in Chengdu found that 70 rosacea patients reddened at lower doses of both UVA and UVB from a solar simulator, a lamp built to imitate sunlight, than 100 healthy people did, and the abstract gives no averages. A Munich laboratory showed in 2014 that LL-37, a peptide found in excess in rosacea skin, increased the inflammatory signal that UVB from a lamp set off in skin cells in a dish. We found no study that exposed people with rosacea to real sun. The NHS advises a sun protection factor (SPF) of 30 or more every day and says to "try to avoid heat, sunlight or humid conditions if possible". 68; 69; 65
Fewer patients are sent south for psoriasis and eczema now that newer drugs control them
In 2020 Petter Gjersvik, a professor of dermatology in Oslo, wrote in the Norwegian medical journal that climate therapy "has become an option for a dwindling number of patients with psoriasis". Oslo's dermatology department had 50 to 60 beds in the 1980s and 14 by then, and most patients were treated at home with biological drugs, hospital UVB, or methotrexate. Applications had fallen, and most who went had "minor or moderate rash upon arrival", by unpublished data he cited. A 2004 evaluation had asked whether the trips were "a welfare scheme or a treatment measure", and its call for a reassessment "met with resistance from patients and came to nothing." 18
Region Syddanmark in Denmark, quoting the national guideline, calls climate therapy "a niche treatment", says stable control "is rarely achieved with climate therapy", and says patients should be offered narrowband UVB or methotrexate first (our translations). In 2022 the Aarhus professor Lars Iversen told a Danish medical magazine that the number of patients treated in Israel was falling, that the effect "often wears off again after some months", and that in quite a few other countries the treatment "has been completely phased out". The Danish psoriasis association now offers stays in Croatia or on the Danish island of Læsø, because trips to Israel are not being arranged. 30; 70; 71
Across seven European eczema registries from 2016 to 2022, 30.1 percent of 5,337 patients had had phototherapy at some point, and 1.7 percent started it when they enrolled, against 75.0 percent who started dupilumab, an injected antibody drug. 72
Since 2023 Norway's adult psoriasis groups have gone for three weeks to Vintersol, a treatment center on Tenerife, paid from a grant in the state budget. The Oslo University Hospital page, updated on 15 September 2026, lists trips into 2027, says the trips are "not an entitlement", and sets the season by skin type (our translations). People of skin type 2, who often burn and sometimes tan, are advised to travel from November to March, and those of type 4 and darker from April to September. Skin type 1, "always sunburned, never brown", "should not apply". 73; 74
Misconceptions
What people believe
- Finsen won a Nobel Prize for curing lupus with sunlight.
- The sun cures psoriasis.
- The Dead Sea filters out the burning rays, so patients can sunbathe there all day.
- The sun helps psoriasis because it makes vitamin D.
- Sun is good for eczema.
- A tan clears acne.
- Skin with vitiligo should never see the sun.
What the studies show
- Finsen treated lupus vulgaris, a tuberculosis of the skin, with concentrated light, most often from a carbon-arc lamp. 7; 9
- Four weeks of Canary Islands sun cleared most psoriasis in 373 Finnish patients, and 49 percent had fully relapsed within six months. 1
- Dead Sea sunlight near 300 nanometers was 21 to 27 percent weaker than in Beer Sheva, and patients from Denmark treated there later had more skin cancer. 2; 3
- In a Tromsø trial, vitamin D pills raised blood vitamin D and did not change psoriasis. 26
- Sun eased eczema in small studies without comparison groups, and light made eczema worse in 120 of 869 people referred for light testing in Manchester. 54; 4
- No trial has tested sunlight on acne. In one survey of 139 patients, about a third each said summer made acne worse, winter made it worse, or the seasons made no difference. 60
- Sun with a dummy lotion repigmented more than half the area in 22.3 percent of vitiligo patches, and a blistering sunburn went with about twice the risk of a vitiligo diagnosis. 47; 5
Questions people ask
Does the sun help acne?
We found no study that followed acne in real sun. In a 1996 survey of 139 patients, about a third said summer made acne worse, a third winter, and a third saw no change. 59; 60
Is the sun good for eczema?
In small studies without a comparison group, two weeks of real sun on Gran Canaria or the Adriatic coast cut eczema scores by 40 percent or more. At a Manchester clinic, light made eczema worse in 14 percent of 869 people referred for testing. 54; 42; 4
Does sunlight help psoriasis?
In 373 Finnish patients given four weeks of Canary Islands sun, the median severity score fell from 4.5 to 0.2, and 49 percent had fully relapsed six months later. About 5.5 percent of people with psoriasis get worse in the sun. 1; 35
Does vitamin D help psoriasis?
Vitamin D pills did not change psoriasis in a four-month Tromsø trial of 122 adults with low vitamin D. The vitamin D creams used for psoriasis are a separate treatment, and the trial's authors describe them as routine. 26
Is the sun good for vitiligo?
In a 1992 study, sun repigmented more than half the area in 22.3 percent of patches painted with a dummy lotion. The NHS warns that "Sunburn is a severe risk" for people with vitiligo and offers phototherapy in hospital. 47; 50
Can a sunburn cause vitiligo?
Among 51,337 American nurses, those who reported a blistering sunburn were diagnosed with vitiligo 2.17 times as often. The burns and the diagnoses both come from the nurses' own questionnaires. 5
Does the sun make rosacea worse?
In a 2002 survey by the National Rosacea Society, 81 percent of 1,066 patients said sun aggravated their rosacea and 75 percent said hot weather did. We found no study of rosacea patients in real sun. 66
Does tanning fade acne scars?
We found no study of acne scars in the sun. A 2023 review says ultraviolet can leave dark and red marks after spots heal, and one dermatologist wrote that "just like cream makeup can camouflage acne, so too can tanning." 62; 75
Do tanning beds help psoriasis?
In a study of 20 adults with no comparison group, six weeks on a commercial tanning bed lowered PASI from 7.96 to 5.04, and 7 had mild burns. Of 617 tanning-bed users in a survey of National Psoriasis Foundation subscribers, 62 percent had started in order to treat their psoriasis. The foundation "does not support the use of indoor tanning beds as a substitute for phototherapy". 76; 77; 78
Does sunlight help seborrheic dermatitis?
We found no study of seborrheic or perioral dermatitis in real sun. In a lamp study of 18 people with severe seborrheic dermatitis, narrowband UVB improved all of them, and all relapsed a median of 21 days later. 79
What we do not know
We found no trial that sent people with psoriasis, eczema, or vitiligo into the sun and compared their skin with that of people who stayed home. The trips combine sun with heat, sea bathing, rest, time off work, and the company of other patients, and the Oslo authors could not rule out that stress reduction helped. In 1993 the Finnish team wrote that placing heliotherapy among other treatments "would require cross-over comparisons, in single patient populations". No one has formally studied how long remission lasts after climate therapy, the American guideline notes. 19; 1; 21
Skin cancer after sun trips has been counted in one registry study that we found, of Danish patients at the Dead Sea, and it could not separate the trips from the rest of their ultraviolet. None of the Canary Islands series we found followed patients for cancer. 3
For acne and rosacea we found no study of patients in real sun, and for seborrheic and perioral dermatitis we found only a lamp study. Nobody has compared times of day for sunning vitiligo. Whether the Perth babies with eczema got less sun because of their rash, or got the rash after less sun, is unknown. 79; 56
Why sun clears psoriasis in most patients and brings it on in a few, most of them women carrying the same immune gene variant, has not been explained. 37
Key studies
- Finsen, 1902, Copenhagen. Carbon-arc lamps and lenses. 412 of 804 patients with lupus vulgaris cured. 10
- Goeckerman, 1925, Mayo Clinic. Coal tar and a quartz lamp, in hospital, for psoriasis. 13
- Parrish and colleagues, 1974. A methoxsalen pill and a UVA lamp, the first PUVA trial. 15
- Parrish and Jaenicke, 1981. Monochromator. Wavelengths from 296 to 313 nanometers cleared psoriasis, and shorter ones only reddened skin. 16
- Abdel-Fattah and colleagues, 1982, Cairo. Khellin or dummy tablets, then real sun. New pigment in 23 of 30 on khellin and 0 of 30 on the dummy. 46
- Abels and Kattan-Byron, 1985, Dead Sea. Real sun. 85.5 percent of 110 psoriasis patients cleared or much improved. 27
- van Weelden and colleagues, 1988. Lamps. The TL-01 narrowband tube beat the older tube in 9 of 10 patients. 17
- Orecchia and Perfetti, 1992, Pavia. Khellin or dummy lotion, then real sun. 24.9 against 22.3 percent of patches repigmented more than half. 47
- Snellman and colleagues, 1993, Canary Islands. Real sun. 373 Finnish psoriasis patients, median score 4.5 to 0.2, 49 percent fully relapsed by six months. 1
- Schuh and colleagues, 1993, Davos. Real sun, assigned by chance. 53 eczema patients, and the outcome was bicycle performance. 55
- Stern and colleagues, 1997 and 1998, United States. PUVA lamps. More squamous cell carcinoma with more treatments, and more melanoma after 15 years. 33; 32
- Snellman and colleagues, 1998, Finland. The cost of a four-week trip. 22
- Frentz, Olsen, and Avrach, 1999, Denmark. Cancer registry. 1,738 Dead Sea patients with 4.2 and 10.7 times the expected skin carcinomas. 3
- Even-Paz and Efron, 2003, Dead Sea. Real sun with a measured dose. Three hours a day worked from March to November. 31
- Cohen and colleagues, 2008, Dead Sea. An insurer's audit of 85 patients. More than three hours of sun predicted improvement, and time in the water did not. 28
- Vähävihu and colleagues, 2008, Gran Canaria. Real sun. Eczema scores fell from 34 to 9 and from 30 to 9 in two weeks. 54
- Hearn and colleagues, 2008, Tayside. Narrowband UVB lamps. No link with skin cancer in 3,867 patients. 34
- Rutter and colleagues, 2009. UVA lamp. Severely photosensitive psoriasis, 19 of 20 patients women. 37
- Søyland and colleagues and Heier and colleagues, 2011, Gran Canaria. Real sun with biopsies. Immune changes in the skin and blood within two days. 19; 23
- Aggarwal and colleagues, 2013, New Delhi. Psoralen with real sun against psoralen with a lamp, assigned by chance. Similar results at less than half the cost. 41
- Teulings and colleagues, 2013. Postal survey. Vitiligo patients had about a third of their partners' odds of skin cancer. 51
- Dunlap and colleagues, 2017. Nurses' questionnaires. A blistering sunburn went with 2.17 times the risk of vitiligo. 5
- Rueter and colleagues, 2019 and 2021, Perth. Real sun measured on babies. Less midday sun in babies who had eczema. 56; 57
- Rutter and colleagues, 2022, Manchester. Lamp tests. Light made eczema worse in 14 percent of 869 people referred. 4
- Kudish and colleagues, 2022, Dead Sea. Meters and a spectroradiometer from 1996 to 2019. 2
- Jenssen and colleagues, 2023, Tromsø. Vitamin D pills against dummy pills. No change in psoriasis. 26
- Terzić and colleagues, 2023, Montenegro. Real sun. Eczema scores 40 percent lower after two weeks. 42
Definitions
- Actinic folliculitis. An eruption of acne-like pustules on the upper body a few days after the first strong sun of the year. Also called acne aestivalis.
- Action spectrum. A curve showing how strongly each wavelength of light produces an effect, such as reddening skin or clearing psoriasis.
- Atopic eczema. Also called atopic dermatitis. A common condition of itchy, dry, inflamed skin, most common in young children.
- Climate therapy. Also called climatotherapy. A stay of several weeks in a sunny place to treat skin disease, combining sunbathing with sea bathing, rest, and education.
- Confidence interval. The range in which the true value probably lies, given the size of a study. A 95 percent confidence interval is the usual one.
- Dendritic cell. An immune cell in the skin that starts and keeps up inflammation.
- Dithranol. An older psoriasis ointment, also called anthralin.
- DLQI. The Dermatology Life Quality Index, a questionnaire score of how much a skin disease affects daily life.
- EASI. The Eczema Area and Severity Index, a standard eczema score.
- Enkephalin. One of the body's own opioid messengers, found in skin.
- Erythema. The medical word for redness of the skin.
- Erythroderma. Redness and inflammation over most of the skin.
- Etretinate. A vitamin A drug taken by mouth for severe psoriasis.
- Hazard ratio and odds ratio. Ways of comparing how often something happens in two groups. 1.0 means no difference, and 2.0 means twice as often.
- Heliotherapy. Treatment with natural sunlight.
- Interleukins. Messenger proteins of the immune system, such as IL-1beta and IL-17, that drive inflammation.
- Keratinocyte. The main cell of the outer skin.
- Khellin. A light-sensitizing chemical from the plant Ammi visnaga, used with sun or lamps for vitiligo.
- Lupus vulgaris. Tuberculosis of the skin, usually of the face. It is a different disease from lupus erythematosus.
- Meta-analysis. A study that pools the results of earlier studies into one estimate.
- Methoxsalen. A psoralen, also called 8-methoxypsoralen, taken by mouth or put on the skin before UVA or sun.
- Minimal erythema dose (MED). The smallest dose of ultraviolet that leaves a patch of skin just visibly red a day later.
- Monochromator. An instrument that picks out one narrow band of wavelengths from a light source.
- Narrowband UVB. Ultraviolet B from lamps with a narrow peak at 311 to 312 nanometers, used in hospitals for psoriasis, eczema, and vitiligo.
- PASI. The Psoriasis Area and Severity Index, the standard psoriasis score, from 0 to 72.
- Photoaggravated eczema. Atopic eczema that light makes worse.
- Polymorphic light eruption. An itchy rash that appears hours to days after sun, mostly in spring and early summer.
- Psoralen. A light-sensitizing plant chemical, such as methoxsalen, taken by mouth or put on the skin before UVA.
- Psoriasis. A long-term skin disease with red, thickened, scaly patches.
- PUVA. Psoralen followed by UVA from a lamp.
- PUVAsol. Psoralen followed by sunlight.
- Randomized trial. A trial in which chance decides who gets which treatment.
- Regulatory T cell. A white blood cell that damps down immune reactions.
- Rosacea. A long-term condition that mainly affects the face, with redness, flushing, and sometimes pimples and visible blood vessels.
- SCORAD. SCORing Atopic Dermatitis, a standard eczema severity score.
- Solar simulator. A lamp built to imitate the spectrum of sunlight.
- Spectroradiometer. An instrument that measures light one wavelength at a time.
- Standard erythema dose (SED). A fixed amount of sunburning ultraviolet, the same for everyone, used to report doses measured by meters.
- Stratum corneum. The dead outer layer of the skin.
- Urocanic acid. A molecule in the outer skin that changes shape when ultraviolet reaches it.
- UVA. Ultraviolet from 315 to 400 nanometers, most of the ultraviolet that reaches the ground.
- UVB. Ultraviolet from 280 to 315 nanometers. It does most of the burning.
- Vitiligo. A condition in which the immune system destroys pigment cells and patches of skin turn white.
Statistics
Among 27 psoriasis patients given four weeks of real sun, the psoriasis severity index fell by a median 96% in the excellent-response group and 74% in the fair-or-good group. 25
The psoriasis patients sent to the Spanish Canary Islands in October and November 1989 sunbathed 0.5 to 1 hour a day at the start, rising to 4 to 6 hours a day within the first week. 25
In 373 psoriasis patients given four weeks of real sun, the median psoriasis severity index fell from 4.5 to 0.2. 1
After four weeks of real sun in the Canary Islands, 84% of 373 psoriasis patients had improved by at least 75% on the severity index, and 22% were completely clear of lesions. 1
After two weeks of real sun, the median psoriasis severity index of 373 patients had fallen from 4.5 to 1.5; 30% had improved by at least 75%, and 3% had worsened. 1
Psoriasis improved by less than 50%, or got worse, in 3% of 373 patients after four weeks of real sun. 1
Psoriasis patients in the Canary Islands built up to 6 hours of sunbathing a day around noon, on one schedule for skin type II and another for skin types III and IV, in March, April or November of 1986 to 1989. 1
In the 129 psoriasis patients who had arthritis at the start, the median arthritis index fell from 6 to 2 during four weeks of real sun. 1
Six months after the real-sun course, the median arthritis index in 55 psoriasis patients with joint symptoms was 8, no different from their starting value of 6. 1
In 258 patients followed after four weeks of real sun, psoriasis had come back halfway in 41% at 2 months, 69% at 4 months and 78% at 6 months, and had fully returned in 23%, 40% and 49%. 1
After the real-sun course, 271 of 361 psoriasis patients (75%) started another treatment within 6 months, and the median time to that next treatment was 80 days. 1
The median psoriasis severity index of 258 followed patients climbed from 0.3 at the end of real-sun treatment to 1.4 at 2 months, 2.8 at 4 months and 3.1 at the end of follow-up, still below the 4.5 starting value. 1
During four weeks of real sun, 11% of 373 psoriasis patients had mild redness, 6% had sunburn, and 11 patients (3%) had a blistering sunburn; six of those 11 had skin type II and three were taking etretinate. 1
An itching rash appeared in the first days of sunbathing in 2% of 373 psoriasis patients, and 4% put a steroid cream on for a short time for relief. 1
Of 373 psoriasis patients, 22% used some anti-psoriasis medicine during the four weeks of real sun, and 14% used dithranol for a short time. 1
Heliotherapy was stopped in 2 of 373 psoriasis patients: one because erythrodermic psoriasis got much worse, the other because of worsening angina. 1
Alcohol abuse caused temporary breaks from the sunbathing program in 6% of 373 psoriasis patients. 1
Of 373 psoriasis patients chosen for real-sun treatment, 83% had had psoriasis for more than 10 years, and 283 (76%) had already had PUVA. 1
One patient with psoriatic erythroderma treated in the Dead Sea area sunbathed twice a day, starting at 5 minutes and adding 5 to 10 minutes a day up to 4 hours a day of real sun. 29
In this one patient, four weeks of real sun and emollients at the Dead Sea cleared the psoriatic erythroderma completely. 29
By the patient's own report, his skin stayed in remission for 5 months without medicine after six weeks of treatment at the Dead Sea. 29
Ten patients with plaque psoriasis treated for four weeks at the Dead Sea increased their real-sun time from 10 to 30 minutes a day at first to 300 minutes a day or more. 80
Four weeks of real sun and salt baths at the Dead Sea cleared psoriasis at the biopsy site in 10 patients, and the mean enkephalin level in lesional skin fell by 21%. 80
After psoriasis cleared with real sun and salt baths at the Dead Sea, immune cells in the dermis had returned to normal in 2 of the 10 patients. 80
After four weeks of real sun and salt baths at the Dead Sea, non-lesional skin in 8 of 10 psoriasis patients showed slight to moderate immune-cell infiltration, and 5 showed a thickened epidermis. 80
Pooling 112 psoriasis patients from three studies (24 on broadband UVB lamps, 68 on broadband or narrowband UVB lamps, 20 given real sun), the PASI score fell by about 75% on every regimen. 24
All 20 Norwegian psoriasis patients given controlled real sun on Gran Canaria in March improved, and their PASI scores fell by a mean 72.8% after 16 days. 19
Before real sun on Gran Canaria, the 20 psoriasis patients had a mean PASI of 9.8 (median 8.7, range 3.8 to 18.8); 2 had skin type II and 18 skin type III. 19
In lesional skin biopsies from the psoriasis patients given real sun, IL-12p40 gene expression fell in 4 of 4 patients by day 16, and IL-23p19 and IL-17 fell in 3 of 4 on both day 2 and day 16. 19
In blood from all 20 psoriasis patients, skin-homing CLA+ T cells had fallen significantly by day 2 of real sun and stayed low on day 16. 19
On the first day on Gran Canaria, 20 psoriasis patients had 1.5 hours of real sun, an estimated 5.1 SED; the 15-day total was 166 SED. 23
Over 15 days of real sun on Gran Canaria, the psoriasis patients received an estimated cumulative 11.8 J/cm2 of UVB, 464 J/cm2 of UVA, and 170 SED. 23
Seventy per cent of the 20 psoriasis patients reported skin redness after the first day of real sun on Gran Canaria, and none had visible redness on day 16. 23
In frozen biopsies from 5 psoriasis patients, lesional dermis held a median 80 plasmacytoid dendritic cells per mm2 before real sun, against 2 in non-lesional skin, and 16 days of sun reduced them significantly. 23
In frozen biopsies from 5 psoriasis patients, inflammatory CD11c+CD1c- dendritic cells were 20 times as dense in lesional dermis as in non-lesional dermis, fell significantly by day 16 of real sun, and were clearly lower already at day 2. 23
In 24 patients with skin disease in the north of Scotland given four weeks of narrowband UVB lamps between December and March, circulating regulatory T cells rose from a mean 0.5% to 1.6% of T cells. 81
In a trial of psoralen plus real sun (PUVAsol) for plaque psoriasis, 15 of the 20 patients who completed the treatment phase (75%) responded, against 15 of 16 (93.75%) given psoralen plus UVA lamps. 41
With psoralen plus real sun, mean PASI in 20 psoriasis patients fell from 14.4 to 3.77 (a 72.44% reduction); with psoralen plus UVA lamps, 16 patients went from 16 to 1.625 (86.85%). 41
Of the 15 psoriasis patients who responded to psoralen plus real sun, 13 reached a 90% PASI reduction. 41
The sunlight arm took 8-methoxypsoralen (0.6 mg/kg), then two hours later sat in real sun between 11 a.m. and 3 p.m., starting at 5 minutes and adding 5 minutes per sitting up to 30 minutes, three times a week for 12 weeks. 41
Psoralen plus real sun took longer to reach the treatment endpoint than psoralen plus UVA lamps: a mean 9.3 weeks and 27.5 sittings (15 patients) against 7.2 weeks and 21.4 sittings (15 patients). 41
None of the 11 psoriasis patients who finished three months of maintenance with psoralen plus real sun relapsed. 41
Side effects affected 16 of 20 patients (80%) on psoralen plus UVA lamps and 12 of 20 (60%) on psoralen plus real sun. 41
Patients on psoralen plus UVA lamps made a median 26 hospital visits for treatment, against 6 for those on psoralen plus real sun (16 and 20 patients). 41
The total cost per patient was a median US$62.7 for psoralen plus UVA lamps against US$26.8 for psoralen plus real sun. 41
Cost per percentage point of PASI improvement was US$0.72 with psoralen plus UVA lamps and US$0.37 with psoralen plus real sun. 41
In 46 plaque psoriasis patients who put a gel on two plaques before sunbathing at home, the median local severity score fell from 6.0 to 2.5. 82
The home-sunbathing psoriasis patients were told to sunbathe for 15 to 30 minutes three to five times a week, between 8:30 and 10:30 a.m. or 3:30 and 6:30 p.m., with sunscreen on the rest of the exposed skin. 82
Of the psoriasis patients using the gel before home sunbathing, scaling had stopped in 40 by the third visit and in the remaining 4 by the fourth. 82
In 44 plaque psoriasis patients on narrowband UVB lamps, the body side treated with the gel ended with a median local severity score of 1.0 against 2.0 on the untreated side, from 7.0 at baseline. 82
Twenty-seven psoriasis patients in Montenegro sunbathed individually 3 to 4 hours a day for 14 days between June and September 2020, avoiding the hours of strongest sun. 43
In 27 psoriasis patients given 14 days of real sun, the mean PASI was 11.31 before, 7.28 after two weeks, and 8.6 three months later. 43
All 27 psoriasis patients improved after 14 days of real sun, but none cleared completely. 43
The mean quality-of-life score (DLQI) of 27 psoriasis patients was 12.00 before 14 days of real sun, 7.85 two weeks later, and 10.85 three months later. 43
In one 32-year-old Indian man with skin type V and segmental vitiligo of 15 years, 12 weeks (36 sessions) of real sun through a band-pass filter cream repigmented more than 75% of the patch on the back, more than 50% on the side of the abdomen, and less than 25% on the front. 49
In the same patient, the first islands of repigmentation appeared at week 4, after 12 sessions of sun through the filter cream, and the repigmentation held 12 weeks after treatment stopped. 49
The patient developed excessive redness on the side of his abdomen twice during the filter-cream sun treatment, after long midday sun exposure in equatorial countries. 49
In adults with atopic dermatitis given two weeks of real sun, the median SCORAD fell from 34 to 9 in the January group (8 patients) and from 30 to 9 in the March group (11 patients). 54
Two weeks of real sun improved atopic dermatitis by 74% on SCORAD in the January group (8 patients) and by 57% in the March group (11 patients). 54
On the first day, atopic dermatitis patients with skin type II or severe disease (8 patients) sunbathed 15 minutes and the rest 30 minutes, without sunscreen, adding 15 minutes a day up to 2 hours of real sun. 54
In the four atopic dermatitis patients who started with high vitamin D, SCORAD fell from a range of 22 to 48 to a range of 0 to 7 after two weeks of real sun. 54
In the March group of atopic dermatitis patients (11), a higher personal real-sun UV dose went with a larger SCORAD improvement (r = 0.67); no such link appeared in the January group. 54
Patients with moderate to severe atopic dermatitis on the Montenegrin coast took real sun 3 to 4 hours a day, without sunscreen, for two weeks in July or August 2021. 42
In 24 patients with atopic dermatitis, the mean SCORAD was 25.91 before two weeks of real sun, 15.13 just after, and 19.30 three months later. 42
In the 24 atopic dermatitis patients, SCORAD was 40% lower than baseline after two weeks of real sun and still 31.1% lower three months later. 42
The mean EASI score of 24 atopic dermatitis patients (20.92 at baseline) fell by 49% after two weeks of real sun and was 31% below baseline three months later; 2 patients reached zero. 42
One of 24 atopic dermatitis patients cleared completely after two weeks of real sun. 42
The mean quality-of-life score (DLQI) of 24 atopic dermatitis patients was 11.42 before two weeks of real sun, 6.92 after, and 8.29 three months later. 42
The mean itch score of 24 atopic dermatitis patients was 1.42 before two weeks of real sun and 1.00 three months later. 42
The daily UV index during the two weeks of real sun ranged from 6 to 9 for the atopic dermatitis patients. 42
Of 19 patients with atopic dermatitis tested with UVB lamps, all had a normal MED, but 3 (15.7%) developed abnormal skin reactions 24 to 72 hours after provocation. 83
All 3 atopic dermatitis patients who reacted to UVB lamp provocation came from the 7 of 19 who reported sun sensitivity; none of those without such a history reacted. 83
None of the 19 atopic dermatitis patients reacted to pure UVA from lamps at doses up to 9 J/cm2. 83
Among infants who wore UV dosimeters to age 3 months, the 16 diagnosed with eczema by 6 months had received a median 555 J/m2 of UV, against 998 J/m2 for the 64 without eczema. 56
The 82 infants with usable dosimeter data received a median 952 J/m2 of real-sun UV from birth to 3 months, usually on the face, hands and arms. 56
By 6 months, 35 of the 173 infants seen at that age had doctor-diagnosed eczema, and the rate did not differ between those given vitamin D drops and those given placebo. 56
Eczema was the most common allergic disease in the trial children, affecting 81 of 164 (49.1%) by age 2.5. 57
Children with eczema by age 2.5 had received a median 747 J/m2 of real-sun UV on dosimeters in their first 3 months, against 1204 J/m2 for children without eczema. 57
Among 164 trial children followed to age 2.5, those who sometimes wore sunscreen had higher odds of eczema (odds ratio 1.57) than those who always or never did; all sunscreen used was SPF 50. 57
In 20 volunteers (10 with atopic dermatitis, 10 without) given 2 MED from a solar simulator on buttock skin, pretreatment with pimecrolimus, a steroid cream or the cream base did not significantly change DNA damage at 1 or 24 hours, and atopic and non-atopic skin did not differ. 84
Of 30 vitiligo patients given khellin with real sun, 23 (76.6%) repigmented to some degree and 5 repigmented 90 to 100%; none of 30 placebo patients repigmented. 46
In the khellin trial, 60 vitiligo patients took khellin or placebo daily for 4 months and then 15 minutes of real sun, 45 minutes after the dose, between 11 a.m. and 3 p.m. 46
Repigmentation from khellin plus real sun did not recede in the year of follow-up after the drug was stopped, and no side effects were seen in the 30 treated vitiligo patients. 46
Over vitiligo patches, the thicker stratum corneum (mean 21.2 micrometres) gave a predicted 1.06 SED of sunburn protection, not significantly different from normal stratum corneum. 85
A 3-year-old boy with vitiligo, treated in Ethiopia with methoxsalen solution and real sun starting at 5 minutes and adding 1 minute per treatment, partly repigmented his eyelid within a month. 48
Three months after the 3-year-old stopped psoralen plus sunlight, the repigmented areas had lost their pigment again. 48
A 15-year-old with segmental vitiligo using topical methoxsalen every other day with 5 minutes of real sun, among other treatments, had 4 to 5 small spots of repigmentation after two months. 48
One 50-year-old woman with vitiligo, taking Brosimum extract and topical khellin before sun three times a week, began at 2 minutes of real sun and reached skin redness at 5 minutes. 86
After one year of the extract, khellin and real-sun routine, with visits every three months, the woman's vitiligo had clearly improved. 86
In one 31-year-old man, sterile pustules on the upper body came back every year for 4 years, each time 48 to 72 hours after the first real-sun exposure of the year. 64
In the same patient, about 15 minutes of real sun was enough to set off an outbreak, and longer exposure brought more pustules over a larger area. 64
His sun-induced pustules cleared without scars in 5 to 7 days, and more sun did not bring a new outbreak unless 1 month or more had passed. 64
Two years after he was first seen, the man had to re-expose himself to sun within about 2 to 3 weeks of the first outbreak to avoid another one. 64
In cultured human keratinocytes given 50 mJ/cm2 of UVB from a lamp, LL-37, the peptide found in excess in rosacea skin, increased the UVB-driven release of the inflammatory signal IL-1beta. 69
In 48 healthy adults with skin type III or IV, forearm skin needed a mean 20 minutes 29 seconds of real sun to reach one MED, a mean dose of 130.48 mJ/cm2. 44
Of 59 psoriasis patients randomized, 36 (61%) finished 12 weeks; all 10 dropouts from the psoralen-plus-real-sun arm (30 patients) stopped attending, while the psoralen-plus-UVA-lamp arm (29) lost 4 patients to erythroderma or severe phototoxicity and 9 who stopped attending. 41
Of the 24 atopic dermatitis patients given two weeks of real sun, 66.7% had skin type II and none had skin type IV. 42
Of 373 psoriasis patients sent for real-sun treatment, 70% had plaque psoriasis, 25% guttate, 4% erythrodermic and 1% flexural, and 47% reported joint symptoms. 1
The heliotherapy program ran nine four-week sunbathing periods with 33 to 45 psoriasis patients each, supervised by a dermatologist, two or three nurses and a sports-and-leisure leader. 1
Psoralen plus UVA lamps worked faster than psoralen plus real sun: mean PASI fell 43.92% against 29.13% at 2 weeks and 70.8% against 50.2% at 4 weeks (16 and 20 patients). 41
At the final visit of the home-sunbathing psoriasis group, 1 patient reported mild and 2 moderate burning, and one other patient had quit because of burning. 82
The atopic dermatitis patients sunbathed on Gran Canaria in two groups: 11 patients from 24 January to 4 February and 12 from 12 March to 26 March. 54