Jørgen Lock‐Andersen, F. de Fine Olivarius, Merete Hædersdal, Thomas Poulsen, Hans Christian Wulf
Skin Research and Technology · 1999
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Abstract
Aims: To investigate the relationships between epidermal thickness, age, skin pigmentation and UV sensitivity in sun‐exposed skin and skin not exposed to the sun in healthy people without skin cancer or skin diseases. Methods: Phototesting with a xenon arc solar simulator was performed in 137 healthy Caucasians in buttock skin un‐exposed to UV (27 children, 34 young adults and 32 older adults) and in skin of the back exposed to UV (44 young adults). The pigmentation of the phototest sites was measured objectively by a skin reflectance spectrometer before phototesting. Thickness of the stratum corneum and the cellular epidermis were measured in skin biopsies from the phototest sites. All measurements were performed in the winter and spring months. Results: Stratum corneum and cellular epidermis were thinner at the back than at the buttocks (P<0.01). Thickness of the stratum corneum at the back or the buttocks was not related to the degree of skin pigmentation (P=0.62 and P=0.20, respectively). Thickness of the stratum corneum at the buttocks was unaffected by gender (P=0.42) and age (P=0.83) whereas cellular epidermis decreased with age (P<0.01) and was thinner in females than in males (P<0.01). In spite of the higher pigmentation at the back than at the buttocks, the minimal erythema dose (MED) was lower at the back than at the buttocks (x=2.7 and x=2.2 SED's, respectively; P=0.04). Given the same degree of skin pigmentation, there was no difference in the MED in buttock skin in children, young adults and older adults un‐exposed to UV (P= 0.61). Prediction of the MED in un‐exposed buttock skin and in exposed skin of the back by a theoretical model based on an exponential function of the measured skin pigmentation was found to provide good estimates of the MED determined by phototest. Conclusion: Skin pigmentation at un‐exposed buttock skin can reliably predict the constitutive UV sensitivity in healthy Caucasian children and adults and is recommended in surveys where phototesting cannot be performed.