Background: The manner in which consumers apply sunscreens is often inadequate for ultraviolet protection according to the labeled sun protection factor (SPF). Although sunscreen SPFs are labeled by testing at an application density of 2 mg/cm(2), the actual protection received is often substantially less because of consumer application densities ranging from 0.5 to 1 mg/cm(2). High-SPF sunscreens may provide more adequate protection even when applied by consumers at inadequate amounts.
Objective: We sought to measure the actual SPF values of various sunscreens (labeled SPF 30-100) applied in amounts typical of those used by consumers.
Methods: Actual SPF values were measured on human volunteers for 6 sunscreen products with labeled SPF values ranging from 30 to 100, applied at 0.5, 1.0, 1.5, and 2.0 mg/cm(2).
Results: There was a linear relationship between application density and the actual SPF; sunscreens with labeled SPF values of 70 and above provided significant protection, even at the low application densities typically applied by consumers. Sunscreens labeled SPF 70 and 100 applied at 0.5 mg/cm(2) provided an actual SPF value of, respectively, 19 and 27.
Limitations: The study was conducted in a laboratory setting under standardized conditions and results are extrapolated to actual in-use situations.
Conclusion: Sunscreens with SPF 70 and above add additional clinical benefits when applied by consumers at typically used amounts, by delivering an actual SPF that meets the minimum SPF levels recommended for skin cancer and photodamage prevention. In contrast, sunscreens with SPF 30 or 50 may not produce sufficient protection at actual consumer usage levels.
Copyright © 2012 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.