Protection against long ultraviolet and/or visible light with topical dihydroxyacetone. Implications for the mechanism of action of the sunscreen combination, dihydroxyacetone/naphthoquinone.

Dihydroxyacetone (DHA) chemically induces long ultraviolet (UV) and/or visible photoprotection into the stratum corneum as demonstrated by (a) long UV protection of albino rats which were psoralen-photosensitized to black fluorescent light and (b) sunlight protection of five patients with long UV and/or visible photosensitivity. Previously, DHA treatment of skin was considered to provide no protection against UV. For clinical use, the combination of DHA and lawsone (2-hydroxy-1,4-naphthoquinone) is preferred to DHA alone, because it provides rapid, positive protection over a range extending from short UV into the visible region of sunlight.