If you have shopped for sunscreen lately you probably saw everything from SPF 15 to SPF 100. American SPF numbers are double the SPF numbers on European products. An American SPF 20 sunscreen is the same as SPF 10 in Europe. It is really getting confusing. One would automatically assume that SPF 30 is twice as protective as SPF 15 and that SPF 80 or 100 would be the best. But it is not really that simple. Let me enlighten you.
The SPF indicates the time a person with sunscreen applied can be exposed to sunlight before getting sunburn relative to the time a person without sunscreen can be exposed. This is usually 20 minutes in spring, without any sunscreen. On any day, someone who would burn after 12 minutes in the sun would expect to burn after 120 minutes if protected by a sunscreen with SPF 10.
Both UVA and UVB contribute to the risk of skin cancer. SPF (Sun Protection Factor) refers to the ability of a sunscreen to block ultraviolet B (UVB) rays, which cause sunburns, but not UVA rays, which are more closely linked to deeper skin damage. Finding a sunscreen that adequately protects against UVA rays is much harder, but just as important. UVA radiation reaches deeper into the skin and contributes to wrinkles and skin cancer risk. Some products labeled "broad-spectrum UVA/UVB protection" do not provide good protection against UVA rays. The best UVA protection is provided by products that contain zinc oxide, avobenzone, and ecamsule. Titanium dioxide gives good protection, but does not completely cover the entire UV-A spectrum, as recent research suggests that zinc oxide is superior to titanium dioxide.
The MOST important factor is using a sunscreen and using it correctly. Limit time in the sun, wear protective clothing and wide brim hats, apply at least one ounce (shot glass) of sunscreen, and reapply sunscreen at a minimum of every two hours, especially after swimming or perspiring.
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