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    In 1978, the FDA Advisory Panel proposed both indoor and natural sunlight SPF testing methods but reverted to indoor testing only in 1993. Today's sunscreen sun protection and broad-spectrum claims are based on mandated clinical tests using solar simulators and in vitro spectrophotometers. This research evaluated the protection of 10 high-SPF (30-110), broad-spectrum sunscreen products, as well as 6 sun-protective fabrics against natural sunlight in Arequipa, Peru. Each of the 17 subjects was exposed to natural sunlight for 1 h and 59 min under clear skies, with temperatures and humidity similar to those in an indoor clinical laboratory. Test sites were photographed 16-24 h later. Four dermatologists evaluated the photographs for erythema and persistent pigment darkening (PPD). Perceptible sun-induced skin injury (sunburn and/or pigmentation) was detected at 97% of the sunscreen-protected scores. The most sun-sensitive subjects obtained the least erythema protection. The higher the SPF was, the higher the erythema protection, but the intensity of PPD was also higher. The 2 sunscreens using only FDA-approved sunscreen filters rated 30 SPF and 45+ SPF performed poorly: Eighty-one percent of the 136 scores were graded 1 minimal erythema dose or higher erythema, achieving, at a maximum, SPF of 5-7 in natural sunlight. Sun-protective fabrics tested provided excellent sun protection. The erythema and PPD observed through the sunscreens in less than 2 h are incongruous with the broad-spectrum, high-SPF sunscreen claims. Reapplying these sunscreens and staying in the sun longer, as stated on the product labels, would have subjected the subjects to even more UV exposure. High-SPF, broad-spectrum sunscreen claims based on indoor solar simulator testing do not agree with the natural sunlight protection test results. © 2021 S. Karger AG, Basel.


    Shaun N G Hughes, Nicholas J Lowe, Ken Gross, Leslie Mark, Bernard Goffe, Hunter Hughes, Curtis Cole. Assessment of Natural Sunlight Protection Provided by 10 High-SPF Broad-Spectrum Sunscreens and Sun-Protective Fabrics. Current problems in dermatology. 2021;55:157-169

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    PMID: 34698042

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