When you think about it, there’s quite a bit of jargon when it comes to protecting your skin from the sun. Sunscreen vs. sunblock. UVA vs. UVB. Chemical vs. physical. Of course, the average person looks for one piece of information on the bottle – SPF.
Let’s start with SPF, or sun protection factor, which ranges from 2 to 50. Most people assume, for example, that SPF 30 sunscreen offers twice as much protection as SPF 15. In reality, SPF 30 absorbs 97 percent of ultraviolet radiation compared to 93 percent for SPF 15. SPF 15 just needs to be reapplied twice as frequently to avoid sunburn.
UVA and UVB are two different ultraviolet wavelengths, or rays. UVA rays play a major role in aging, wrinkling and tanning. UVB rays are the primary cause of sunburn. Both UVA and UVB rays contribute to skin cancer, which is why you want to look for a product that protects against both.
Many people use the terms “sunscreen” and “sunblock” interchangeably. Technically, sunscreen is a chemical lotion that penetrates the skin, absorbs UVB rays, and harmlessly releases their energy. Some newer sunscreens include UVA-absorbing chemicals as well.
Sunblock is a physical lotion that provides broad-spectrum protection against both UBV and UVA light. Physical sunblock sits on the surface of the skin and provide a shield, or physical block, against harmful rays, which are reflected instead of absorbed. Physical sunblock used to be known for its pasty white residue, but newer versions are virtually transparent and not as greasy.
Although we recommend at least SPF 15 to avoid sunburn, don’t get hung up on SPF when choosing sunscreen. The key is to look for a broad-spectrum or full-spectrum sunblock that offers protection from both cancer-causing rays – UVA and UVB. If you’ll be spending time in the water or working outside and sweating, look for a water-resistant product.