Posted on January 19th, 2011 by
According to a study published in the Archives of Dermatology, few daily moisturizers with sunscreen provide adequate protection against ultraviolet A (UVA) radiation.
Ultraviolet radiation is often divided into three types: UVA, UVB, and UVC. Although the sun emits all three types of ultraviolet radiation, only UVA and UVB reach the surface of the earth (UVC and some UVB are blocked by the ozone layer). UVB is the cause of most sunburns and has long been recognized as a cause of skin cancer. UVA—which penetrates more deeply into the skin—was initially thought to be relatively safe. Now, however, it’s recognized that both types of ultraviolet radiation are likely to contribute to skin cancer.1
The sun protection factor (SPF) of a sunblock refers only to protection against UVB. There is currently no standard measure of protection against UVA. Many daily moisturizer creams with sunscreen claim to provide broad-spectrum protection against both UVB and UVA, but the degree of UVA protection is often uncertain.
To explore the extent of UVA protection provided by daily moisturizers, researchers evaluated 29 products that claimed to provide broad-spectrum UV protection.2 The names of the products were not provided, but the products ranged in price from $3 to $64 per ounce.
The researchers focused on protection against long-range UVA1 (340 to 400 nm) radiation. Protection against UVA1 was considered adequate if at least one of the following criteria was met: 1) a combination of avobenzone (>2%) and octocrylene (>3.6%) with or without ecamsule (2%); 2) the presence of zinc oxide (>5%).
The researchers concluded that few of the products provided adequate protection against UVA1 radiation. The researchers note “Until sunscreen labeling clearly defines the degree of UV-A protection, dermatologists should educate their patients and the public to select products with ingredients that contain the appropriate concentrations of avobenzone, octocrylene, and ecamsule and/or zinc oxide.”
1 El Ghissassi F, Baan R, Straif K et al. A review of human carcinogens—Part D: radiation. Lancet Oncology. 2009;10:751-752.
2 Wang SQ, Goulart JM, Lim HW. Lack of UV-A protection in daily moisturizing creams [Research Letter]. Archives of Dermatology. Early online publication January 17, 2011.
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