SPF stands for "Sun Protective Factor." Sounds all-inclusive right? Wrong. SPF protects only against UVB. UVB, the chief cause of skin reddening and sunburn, tends to damage the skin's more superficial epidermal layers. It plays a key role in the development of skin cancer and a contributory role in tanning and photoaging. Its intensity varies by season, location, and time of day. The most significant amount of UVB hits the U.S. between 10 AM and 4 PM from April to October. However, UVB rays can burn and damage your skin year-round, especially at high altitudes and on reflective surfaces such as snow or ice, (or even off dry sand and concrete) which bounce back up to 80 percent of the rays so that they hit the skin twice. This happens even if we are sitting under the shade of a tree or beach umbrella. Yikes!
UVA, which penetrates the skin more deeply than UVB, has long been known to play a major part in skin aging and wrinkling (photoaging), but until recently scientists believed it did not cause significant damage in areas of the epidermis (outermost skin layer) where most skin cancers occur. Studies over the past two decades, however, show that UVA damages skin cells called keratinocytes in the basal layer of the epidermis, where most skin cancers occur. UVA contributes to and may even initiate the development of skin cancers.
Sunscreen Hall of Shame
The Environmental Working Group put together this list of the worst, and most unsafe sunscreens you might be using on yourself and your littles. The spray sunscreens are the worst. Come on folks, by now, everyone should know that toxin-filled aerosols are harmful for human health.
11 of the WORST SPRAY Sunscreens
These sunscreens are aerosol sprays with SPFs above 50+ and the harmful additives oxybenzone and retinyl palmitate.