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John A. Johnson, PhD
Department of Internal Medicine/Dermatology University of Nebraska Medical Center 600 South 42nd St Omaha, NE 68198-4360

Arch Dermatol. 1992;128(3):409.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

To the Editor.—

Kaye et al¹ described the efficacy of opaque photoprotective agents for protection against UV-A and visible radiation, and Sayre et al² elegantly described the optical properties of physical sunscreens. The former report is of special interest, because it appears clinical investigators are now recognizing a point we stressed for many years³: A broad UV-A screen will almost certainly be colored. A screen for visible radiation must, by definition, be colored, preferably a pleasing brown. Physical sunscreens suffer from the same defect as many chemical sunscreens: they rub off or are removed by aqueous fluids.

Browning agents such as dihydroxyacetone (DHA) form a brown color in the stratum corneum that absorbs blue light with overlap into the adjoining UV-A region.³ Thus, DHA covers the window of vulnerability left by chemical sunscreens, ie, long-wavelength UV-A radiation and blue light. Furthermore, the chemically bound color produced . . . [Full Text PDF of this Article]

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