Journal of Clinical & Experimental Dermatology Research
Open Access

UV absorbance of sunscreen products: Concentration dependence and comparison of efficacy using an in vitro technique

14^th International Conference on Clinical and Experimental Dermatology

June 19-20, 2017 Philadelphia, USA

Ariel G Silverman, Kayla S Silverman, Deborah H Markowitz and Eric S Silverman

Metro-West Medical Center, USA

Posters & Accepted Abstracts: J Clin Exp Dermatol Res

Abstract :

When used properly, sunscreens protect skin from the harmful effects of UV radiation. Sun Protection Factor (SPF) is an in vivo technique widely used to compare UVB-blocking ability and is the FDA-approved method of testing products. Sunscreens are tested at a concentration of 2 mg/cm2; however, investigations show that users typically apply insufficient amounts to achieve full protection. Amounts of 0.39 to 1.0 mg/cm2 have been found under natural conditions. The relationship between SPF and concentration has been described as both logarithmic and linear. Furthermore, Consumer Reports recently tested 65 products and found wide variation in efficacy, even when used at the recommended concentration. 43% of products failed to achieve the SPF claim on the label. To shed light on these issues, we measured the UV absorbing properties of 11 SPF- 30 products and compared the concentration dependence using in vitro technique. An ultraviolet spectrophotometer (General UV513AB) was used to measure UV light (�¼W/cm2). UVA/B light was focused on dilutions of each product, (0 to 5 mg/cm2) and the amount of transmitted light measured in triplicate. The absorbance vs. concentration curves are shown in the Figure. The relationship between absorbance and concentration was logarithmic approaching an asymptote at higher concentrations that are commonly applied to skin. Of concern was high variability in absorbance between products at recommended concentrations (coefficient of variance 38% at 2.5 mg/cm2). This in vitro experiment is consistent with previously published in vivo studies suggesting that sunscreens effectively block broad-spectrum UV light, however, there is high variability between brands, and it is essential to use recommended doses because there is a strong relationship between concentration and absorbance.

Biography :

Email: esilverman@pamw.org