Epidermal Permeability Barrier Dysfunction Influences Acute and Chronic Skin Responses to UVA and UVB Radiation

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BACKGROUND: The epidermal permeability barrier is crucial for skin homeostasis and defending against ultraviolet radiation. While it's known that barrier dysfunction is a feature of many dermatoses, how different degrees of barrier dysfunction affect acute and chronic responses to UVA and UVB remains unclear. This study compared erythema and pigmentation responses in skin with different levels of barrier dysfunction. METHODS: Forty-nine healthy female subjects (Fitzpatrick skin types III-IV) were enrolled. Barrier-impaired models were created on one volar forearm by tape stripping; the contralateral forearm served as a control. Both sites received graded doses of UVA and UVB. Skin color was assessed using a spectrophotometer to obtain L* (lightness) and a* (redness) values. Changes (△L, △a) were compared between barrier-impaired and normal skin immediately, 24 h, and 2 weeks after irradiation. RESULTS: The influence of skin barrier integrity on UVA-induced immediate pigment darkening varies with UVA dose: a more compromised barrier correlates with a stronger response at low doses, whereas normal skin exhibits a more pronounced reaction at higher doses. Moderate-to-severe barrier damage led to more pronounced persistent pigment darkening and delayed tanning after UVA. Following UVB exposure, severely impaired skin exhibited more pronounced delayed erythema and post-inflammatory hyperpigmentation than normal skin. CONCLUSION: An intact epidermal permeability barrier contributes to protecting the body from UV-induced damage. Therefore, restoring and maintaining an intact epidermal barrier should be considered a fundamental strategy in photoprotection and the clinical management of disorders associated with barrier dysfunction.

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