Background: Recent accumulating data in the literature have indicated a complex photoprotective role of the epidermis, and the role of melanin as the major epidermal photoprotective mechanism has become debatable.
Aim: Comparative assessment of the photoprotective roles played by different epidermal structures and compounds.
Methods: In total, 64 participants, comprising patients with vitiligo (n = 32) and healthy volunteers (n = 32), with skin phototypes (SPTs) II to V, were enrolled in the study. Areas of skin were delineated; for both lesional and nonlesional skin, the stratum corneum (the SC) was stripped, followed 24 h later by exposure to narrowband ultraviolet B (NB-UVB) irradiation, to measure the minimal erythema dose (MED) in normal, stripped normal, vitiliginous and stripped vitiliginous skin models. These MED values were used to assess the photoprotective role of epidermal structures: melanin, viable epidermis (VE) and the SC.
Results: In the vitiligo group, the MED values were significantly (P < 0.05) different between the skin models, being highest in normal skin, followed by stripped normal, vitiliginous and stripped vitiliginous skin. A similar significance level was found within each SPT for almost all comparisons. There was also a significant (P < 0.001) positive correlation between MED and SPTs. There were also significant (P < 0.05) differences in MED values calculated for epidermal structures, being highest for VE, followed by melanin and then the SC, and there was a significant (P < 0.05) positive correlation between MED and SPTs.
Conclusion: Epidermal photoprotection may extend beyond melanin production, involving several factors such as epidermal layer thickness, optical properties and chromophores. Such a role was perceived to be reactive to UV irradiation, and more efficient in those with higher SPTs.
© The Author(s). CED © 2010 British Association of Dermatologists.