SPF Refers Mainly to the Amount of UVB Protection a Sunscreen Offers
UV radiation reaches the earth in the form of UVB and UVA rays. UVB radiation plays a key role in skin cancer, and SPF refers mainly to the amount of UVB protection a sunscreen offers. An SPF 15 sunscreen blocks 93 percent of UVB radiation, while an SPF 30 sunscreen blocks nearly 97 percent and an SPF 50 sunscreen blocks an estimated 98 percent of UVB rays.
Higher Value SPF
Higher SPF values offer some safety margin, since consumers generally do not apply enough sunscreen. To evaluate SPF, testers apply two milligrams of sunscreen per square centimeter of skin. But in everyday life, most people apply from only 0.5 to one milligram per square centimeter of skin. The actual SPF they achieve is approximately 1/3 of the labeled value.
Downside of Very High SPF Sunscreens
Despite these advantages, there are potential downsides to using products with very high SPF. First, above SPF 50 (which blocks an estimated 98 percent of UVB rays), the increase in UVB protection is minimal. Second, although UVA protection is also important (UVA not only accelerates skin aging, but contributes to and may even initiate skin cancers), SPF mainly measure UVB protection. Individuals applying high-SPF sunscreens may not burn (UVB is the chief cause of sunburn), but without UVA-screening ingredients they can still receive large amounts of skin-damaging radiation.
Europe and Australia UVA Testing Guidelines
Regulatory bodies in Europe and Australia have adopted UVA testing guidelines and measurement standards, and capped the SPF of sunscreens at 50+.
The FDA determined in 2011 that high SPF claims may be “inherently misleading” and the FDA proposed joining most other industrialized nations in capping SPF values at 50-plus.
Products with very high SPF may also encourage individuals to neglect other photoprotective behaviors, like seeking the shade and wearing sun-protective clothing. By preventing sunburn, sunscreens with very high SPF can create a false sense of security, prompting consumers to stay out in the sun longer. Sun damage (for example, UVA damage) can take place without skin-reddening doses of UV radiation, and even the best sunscreens should be considered just one vital part of a comprehensive sun protection regimen.
Sunscreens with SPF no Lower than 30 and no Higher than 50
The American Academy of Dermatology recommends using a product with an SPF of 30 or higher. The importance of using both UVB and UVA protection cannot be emphasized enough. Love Sun Body and Dr. Zickerman suggest sunscreens with SPF no lower than 30 and no higher than 50. In addition to an SPF of 30+, Love Sun Body sunscreens include the following UVA-blocking ingredients: SPF 30 non-nano zinc oxide, SPF 50 non-nano zinc oxide and non-nano titanium dioxide. Love Sun Body sunscreens include both UVA and UVB protection and are labeled broad spectrum (multi spectrum/UVA/UVB protection).