Common Diagnosis
Sunscreens
Sun screens are important in our prevention of skin cancer. However, there seems to be a lot of confusion about sun screens and how they should be used.
First, it is important to know that there are sun screens, and sun blocks. Sun screens use chemicals to filter out the harmful rays of the sun, while sun blocks physically block the harmful rays. Sun screens are generally less occlusive and easier to wear than sun blocks, but they are usually not as effective at protecting the skin.
Next, it is important to know that there are two types of ultraviolet light coming from the sun that we need to protect ourselves from, UVA and UVB. UVA is called the “aging” rays, as they cause premature aging of the skin and have been suspected in causing melanoma, the deadliest form of skin cancer. They do not burn the skin, however, and therefore, they are used in tanning beds, which is why tanning beds are safe only from sun burns, but may actually cause skin cancer. UVB is known as the type of ultraviolet light that causes a sun burn. Most of the sun screens are very effective at blocking UVB which is why when we wear them, we do not get a sun burn.
Now, the SPF on sun screens is a measure of how effective a sun screen or sun block is against UVB. It is not a measure of how effective it is against UVA. So, a high SPF sun screen or sun block will be effective against sun burns, but not against the aging rays of UVA.