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The value of melanin as a sunscreen

Kollias, N.

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doi: 10.1097/01.cmr.0000382753.63001.f0
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Epidermal melanin pigmentation has been considered as a primary absorber of ultraviolet radiation thus providing protection to the underlying epidermal and dermal elements. The absorption spectra of synthetic and extracted melanins provide the evidence why melanin might provide adequate protection in the ultraviolet. The detailed structure of the absorption spectra of epidermal melanin pigmentation in vivo together with the reactivity of melanin precursors and metabolites to ultraviolet A (320-400 nm) and visible (400-700 nm) radiation indicate that epidermal melanin may not be considered simply as passive absorber in the skin that acts as a neutral density filter – i.e. absorbing equally strongly at all wavelengths. A second approach to evaluate the effectiveness of epidermal melanin pigmentation as a filter for ultraviolet radiation is by studying the action spectra for the erythema and pigment reactions of skin to ultraviolet radiation for individuals of different levels of pigmentation. Here we find that epidermal melanin is not a neutral density filter providing no or minimal protection for the induction of erythema at 295 and 315 nm and some protection at 305 and 365 nm. It is necessary therefore to rethink the role of epidermal melanin pigmentation or the ensemble of compounds that make it up (soluble and insoluble melanin, precursors and metabolites etc) and their reactivity in the skin.

© 2010 Lippincott Williams & Wilkins, Inc.