We are so used to seeing words like "sunblock" and "waterproof" on sunscreen labels that we actually believe sunscreens block out the sun or stay put no matter how wet and sweaty we get. But the truth is that no sunscreen can do either. That's why the U.S. Food and Drug Administration has changed rules about labeling. Here are some tips for how to choose and use suncreen.
Get rid of old sunscreen. Yes, there's a shelf life of 3 years, but you don't know when a product first landed on a shelf. Theoretically it's good until the expiration date, if there is one — but that's only if it hasn't been exposed to any extreme heat. I don't know the temperature of your beach bag, but mine gets pretty hot. Better to throw out the old sunscreen and buy a new tube or bottle.
A higher SPF number doesn't necessarily mean more protection. You aren't getting much more benefit with an SPF higher than 30. (Consumer Reports suggests buying 40 SPF or higher, as their tests showed some of the 30's weren't quite 30's). You definitely don't need to buy a 100 SPF product for your child. You are better off buying a hat — or clothing that deflects UV rays.
Buy sunscreen with "broad spectrum" protection. You want to get protection from both UVA and UVB rays.
Even if the label says "water resistant" or "waterproof," you need to reapply it. Check the label for how long the sunscreen is effective when exposed to water or sweat. If there's no information, reapply every 1-2 hours. Actually, that's about how often you should reapply it even if you're not in the water.
Don't buy a product that combines a sunscreen and an insect repellent. Sunscreen should be reapplied frequently, but insect repellents should not. Buy separate products and apply them separately.
Use an ounce of sunscreen per large child or adult. That's about as much as would fill your hand — or a shot glass. You really want to cover all exposed skin well.
Choose lotions over sprays. While sprays seem easier, it's harder to be sure that you are covering all the skin well. Also, there are concerns that breathing in the spray (which is easy to do while spraying it) could be harmful.
Don't buy sunscreen powders. These go on your scalp. They're easy to inhale, so avoid them.
Apply sunscreen before you go out in the sun. That way, you go into the sun protected. Plus, you don't have to worry about children being squirmy or running away from you. If you have small children, apply the sunscreen before you put on their clothes or bathing suits. Then you'll be sure you don't miss any spots.
There is controversy over the safety of some sunscreen ingredients. These include oxybenzone, retinoids and nanoparticles. The Environmental Working Group has a list of 184 sunscreens that meet their safety criteria. You can choose one of those to be on the safe side. However, it's important to know that the American Academy of Dermatology does not believe that those ingredients pose a health risk.
What does pose a health risk is too much sun exposure. Burns during childhood can especially raise the risk of skin cancer later in life. So the most important thing is to buy that sunscreen — and use it often and well.
Claire McCarthy, M.D., a senior medical editor for Harvard Health Publications, is an assistant professor in pediatrics at Harvard Medical School. She is an attending physician and Medical Communications Editor at Children's Hospital Boston.