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Putting Sunscreen to the Test
By Louis Kuritzky, MD
Dr. Kuritzky is Clinical Assistant Professor, University of Florida, Gainesville.
Dr. Kuritzky is a consultant for GlaxoSmithKline and is on the speaker's bureau of GlaxoSmithKline, 3M, Wyeth-Ayerst, Pfizer, Novartis, Bristol-Myers Squibb, AstraZeneca, Jones Pharma, and Boehringer Ingelheim. Peer reviewer Gerald Roberts, MD, Assistant Clinical Professor of Medicine, Albert Einstein College of Medicine, New York, NY, reports no financial relationships relevant to this field of study.
This article originally appeared in the January 29, 2009 issue of Internal Medicine Alert.
Source: Sang SQ, et al. In vitro assessments of UVA protection by popular sunscreens available in the United States. J Am Acad Dermatol 2008;59:934-942.
SPF stands for "sun protection factor," but if FDA recommendations change, the name will soon stand for "sunburn protection factor" because of the recognition that current SPF testing reflects erythema effects of UVA light in the 320-340 nm and UVB light in the 290-320 nm wavelengths, but does not necessarily reflect efficacy for other photodamaging wavelengths. UVA light in the 340-400 nm range is also dermotoxic, but impact of sunscreen on this light component has not previously been included in labeling. In August 2007, the FDA suggested a new rating scale that includes a ratio of UVA 340-400 nm (termed UVA1) to total UV light absorption. Agents that have low efficacy for absorbing UVA1, even though they have good efficacy for other wavelengths, would be rated lower in overall efficacy.
An analysis of 13 OTC sunscreen products using the new FDA criteria found 8 to provide medium protection and 5 to provide high protection. All but one of the selected products had an SPF of at least 30. If the proposed FDA metric becomes widely accepted, consumers will have an opportunity to better appraise the overall efficacy of sunscreen products.