UV-induced immune suppression and sunscreen

Abstract

Sun protection factor (SPF) that measures sunscreen protection against erythema and edema may not be enough to measure a sunscreen's activity against many other biologic reactions induced by ultraviolet radiation (UV). It may be better to evaluate sunscreen efficacy using various tools including immune protection factor (IPF), mutation protection factor (MPF) and protection against photocarcinogenesis. In terms of immune protection, sunscreens protected against UV-induced immune suppression significantly. But protection in some cases was partial and often the IPF of sunscreens were less than the SPF. IPF may differ with various immunological endpoints, and it may be better to use a couple of different assays to measure sunscreen protection more objectively. Sunscreen use protects against most UV-induced non-melanoma skin cancers and actinic keratoses but its activity against melanoma is not clear. More studies with broad-spectrum stable sunscreens and better models for the investigation of malignant melanoma are required.

Alternative methods to evaluate the protective ability of sunscreen against photo-genotoxicity

“…It has recently been suggested that the SPF value may not be a sufficient gauge of a sunscreen's ability to protect against the many harmful biological reactions induced by sunlight. Gill and Kim proposed the Immune Protection Factor (IPF) as a measure of the effectiveness of a sunscreen to protect against UV-induced immune suppression [9]. Ananthaswamy et al proposed the Mutation Protection Factor (MPF) as an estimate of a sunscreen's protective activity, as obtained through the measurement of p53 mutation in the skin of mice irradiated with UVB [10].…”

Exploration of "Alternative" and "Natural" Drugs in Dermatology

“…29,30 Protection against UV-induced skin damage includes avoidance of sun exposure, application of sunscreens, low-fat diets, 31,32 and pharmacologic intervention with retinoids. 33 More recently, green tea extracts have been reported to be beneficial in treating UV-induced photodamage.…”

Photoprotection

“…1 Acute response of human skin to UVB irradiation includes erythema, edema, and pigment darkening followed by delayed tanning, thickening of the epidermis and dermis, and synthesis of vitamin D; chronic UVB effects are photoaging, immunosuppression, and photocarcinogenesis. 2 UVB-induced erythema occurs approximately 4 hours after exposure, peaks around 8 to 24 hours, and fades over a day or so; in fair-skinned and older individuals, UVB erythema may be persistent, sometimes lasting for weeks. 3 The effectiveness of UV to induce erythema declines rapidly with longer wavelength; to produce the same erythemal response, approximately 1000 times more UVA dose is needed compared with UVB.…”