Background: New research has attributed increased significance to the causal link between ultraviolet A (UVA) radiation and immunosuppression and carcinogenesis. In the United States, sunscreens are labeled with only their sun protection factor (SPF) and an imprecise term "broad-spectrum protection." Sunscreen marketing and efficacy evaluations continue to be based primarily on skin redness (sunburn) or erythema. We sought to evaluate the ultraviolet (UV) protection offered by common sunscreen products on the US market using laboratory-measured UV-absorption testing and comparing with computer-modeled protection and the labeled SPF values. This approach enables an investigation of the relationship between the labeled SPF and measured UVA protection, a factor that is ignored in current regulations.
Methods: Fifty-one sunscreen products for sale in the United States with SPF values from 15 to 110 and labeled as providing broad-spectrum protection were tested using a commercial laboratory. All products were evaluated using the ISO 24443:2012 method for sunscreen effectiveness. The final absorbance spectra were used for analysis of in vitro UV protection.
Results: In vitro SPF values from laboratory-measured UV absorption and computer modeling were on average just 59 and 42 percent of the labeled SPF. The majority of products provided significantly lower UVA protection with the average unweighted UVA protection factor just 24 percent of the labeled SPF.
Conclusion: Regulations and marketplace forces promote sunscreens that reduce sunburn instead of products that provide better, more broad-spectrum UV protection. The production and use of products with broad spectrum UV protection should be incentivized, removing the emphasis on sunburn protection and ending testing on people.
Keywords: SPF; UVA protection; UVA protection factor; erythema; general dermatology; melanoma; sunscreen; ultraviolet A.
© 2021 The Authors. Photodermatology, Photoimmunology & Photomedicine published by John Wiley & Sons Ltd.