Chemical or Mineral?
Chemical sunscreens with ingredients like avobenzone and octocrylene work by absorbing UV radiation and reducing how much penetrates into your skin, explains Elizabeth Hale, MD, a dermatologist in NYC and senior vice president of the Skin Cancer Foundation. Mineral formulas contain things like titanium dioxide and zinc oxide, which stay on top of the skin and deflect the UV rays. Both are effective, and many formulas even contain a mix of the two. If you have sensitive skin, better to opt for a mineral sunscreen since it doesn’t have any chemical reaction with your skin. NOTE: some popular vacation destinations – like Hawaii and parts of Mexico – are banning certain chemical formulas that are thought to have bleaching effects on coral reefs.
Shelf life varies from 2-3 years, depending on the formula you choose. Look at that date before purchasing, and continue to pay attention to it. The reason: Sunscreens don’t always show obvious signs they are past their prime. Dr. Hale also advises keeping track of where your bottle has been, saying “exposure to UV light and heat can degrade a product a lot faster”. Additionally, if you keep sunscreen in the bathroom, humidity can cause issues as well. Best to replace sunscreen annually.
The SPF (sun protection factor) meaures how well the sunscreen blocks out UVB rays – which are primarily what causes sunburns. The number tells you how long it would take to redden your skin vs. the amount of time without it. For example, with SPF 15, it will take you 15 times longer to burn than if you were wearing nothing. So what number should you aim for? You want to choose at least SPF 30, says Melanie Palm, MD, A board-certified dermatologist in Solana Beach, California. Anything higher is a bonus!
UVB rays primarily cause sunburn. The sun’s UVA rays penetrate deeper than UVB and play a role in causing wrinkles. Look for a bottle has says “broad spectrum” or UVA/UVB explains Dr. Hale.