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To the Editor.—
Dr. Fusaro's statement that for the clinical testing of sunscreening preparations ". . . any test procedure other than sunlight exposure seems superfluous." is not borne out by the observations he cites, nor by practical experience. There are several major flaws in his arguments:The assumption that β-carotene is primarily effective due to absorption of light in the vicinity of the Soret band is incorrect. The study he quotes by Kobza et al disproves this assumption, nor has such a claim been made by Dr. Matthews-Roth or her colleagues. Thus, β-carotene cannot be likened to the vast majority of agents used for protection of the skin against the effects of ultraviolet (UV) radiation below 320 nm (ie, the "sunburning" region), all of which act simply as filters.The assumption that the xenon arc solar simulator described in the report on UV light sources is a reasonable instrument for quantitative
Urbach F. Limited Usefulness of Artificial Light Sources-Reply. Arch Dermatol. 1975;111(3):395-396. doi:10.1001/archderm.1975.01630150115019