SPF—What does it have to do with UVA and UVB?
UV stands for ultraviolet, as in ultraviolet radiation. UVA is a type of radiation that causes skin to tan. UVB radiation causes skin to burn. According to The Skin Cancer Foundation, UV radiation in general is the main cause of non-melanoma skin cancers. It also factors into the development of melanoma, the deadliest of skin cancers.
We're exposed regularly to UV radiation from the sun—even on cloudy days and even in the shade—because, according to the Melanoma Education Foundation, reflective surfaces such as snow, sand, water and concrete reflect the UV rays back upward, right onto our skin. And since UVA rays pass through glass, our skin is also vulnerable to UV radiation indoors and in cars.
SPF Protects Against UVBs—but not UVAs
SPF stands for the Sun Protection Factor scale that rates the level of sunburn protection in sunscreen products—but only against the UVB rays, which cause sunburn. Although UVA rays don't cause sunburn—only tanning—they're still dangerous. Even tanning damages skin and can cause the formation of skin cancer.
SPF 15 screens 93 percent of the sun's UVB rays. SPF 30 screens 97 percent. SPF 50 screens 98 percent. No sunscreen provides 100 percent protection. While The Skin Cancer Foundation recommends that everyone use products with a minimum of SPF 15 for adequate protection, The American Academy of Dermatology recommends using products with a minimum of SPF 30.
Additional Ingredients Protect Against UVBs and UVAs
For the best overall protection, according to the American Academy of Dermatology, buy "broad spectrum" products that contain SPF and at least one of the following ingredients: avobenzone, cinoxate, ecamsule, menthyl anthranilate, octyl methoxycinnamate, octyl salicylate, oxybenzone, sulisobenzone, titanium dioxide or zinc oxide—these ingredients are believed to be effective against both UVB and most UVA rays.
For more information on how to protect yourself from skin cancer, visit The American Cancer Society, The Skin Cancer Foundation, The American Academy of Dermatology and The Melanoma Education Foundation.