Each year we are surprised that Consumer Reports (CR) magazine does not recommend to its subscribers a mineral sunscreen. Such products, containing active inorganic ingredients zinc oxide and/or titanium dioxide, act by ultraviolet (UV) reflection and thus might be expected to be more efficient and stable than organic chemical sunscreens which act by UV absorption and can quickly become saturated or break down. Additionally, some chemicals in organic sunscreens may cause contact dermatitis and harm marine life; specifically, oxybenzone can react with chlorine, producing hazardous by-products that can concentrate in swimming pools and wastewater treatment plants.1 Ultimately, the ability of sunscreen to reduce skin cancer risk relates to prevention of UV-induced DNA damage. A recent review of sunscreen-mediated prevention of DNA damage identified 10 studies demonstrating sunscreen efficacy; however, none involved direct comparisons of chemical vs. mineral sunscreens.2 In one study, a zinc and titanium-based sunscreen completely attenuated induction of cyclobutene pyrimidine dimers and p53 in sun-exposed skin at 24 hours.3 We took a closer look at how CR evaluates sunscreens, and identified several potential flaws in their testing methods and scoring criteria which may disadvantage mineral-based products.
CR rates sunscreens based on three primary criteria: sun protection factor (SPF) as a measure of UV-B protection, UV-A protection, and variation from the product-advertised and CR-determined SPF rating.4 CR assesses SPF by applying sunscreen to six areas on participants’ backs followed by submersion in water for either 40 or 80 minutes, depending on the water resistance claims of the manufacturer. The six spots are then exposed to different intensities of UV-B and examined one day later for erythema. UV-A protection is assessed by irradiating plastic plates covered with sunscreen and measuring the amount of UV-A transmission. CR also assesses sensory factors such as scent and skin feel, but does not specify how these or any of the primary criteria are weighted in determining their final score.
Mineral sunscreens typically have low advertised SPF ratings (e.g. 30+) and thus may be disadvantaged compared to most chemical sunscreens with higher SPF, although an SPF of 30 theoretically provides 97% UV protection. It is unclear to what extent submersion in water impacts the SPF of various products. Preferably, as with FDA testing,5 water resistance claims should be assessed separately from SPF with submersion testing. Consumers may be better served by CR having a separate category and ranking list for mineral- and chemical-based products, and by reviewing similar numbers of mineral and chemical sunscreens. In addition, there are sunscreens containing both mineral and chemical components, and it would be helpful to include some of these products in future reviews. It would also be helpful to have ratings for each of the criteria to allow consumers to assess tradeoffs between the different characteristics of a sunscreen product. Finally, testing of other product claims that may influence consumer preference, such as being non-comedogenic, could be considered. We contacted CR but were not provided with more information regarding their testing procedures and scoring methods. In addition to scoring details, we do not have key information on the participants (e.g. number, gender, age, skin types), amount of sunscreen used or the application process, and how subjective factors like scent and feel (which are often barriers to sunscreen use) were treated. We appreciate the value of CR providing ratings of sunscreen products which may help consumers find a sunscreen product they enjoy using and thereby increase sunscreen use in the U.S. population. However, greater transparency and scientific rigor in sunscreen testing will allow consumers to make better informed choices.
Acknowledgments
D.G. is supported by the Huntsman Cancer Foundation and the Department of Dermatology at the University of Utah. S.A.L. is supported by the John D. Gray Endowed Chair in Melanoma Research through Knight Cancer Institute and the Department of Dermatology at Oregon Health & Science University.
Abbreviations
- CR
Consumer Reports
- SPF
sun protection factor
- UV
ultraviolet
Footnotes
The authors declare no conflicts of interest.
References
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