While you should use sunscreen every day of the year, it’s even more important during the summer, when the days are longer, the sun is stronger, and it’s easier to spend more time outdoors. When choosing a sunscreen, read the label before you buy it. US Food and Drug Administration regulations require the labels to follow certain guidelines:
Choose a sunscreen with “broad-spectrum” protection. Sunscreens with this label protect against both UVA and UVB rays. All sunscreen products protect against UVB rays, which are the main cause of sunburn. But UVA rays also contribute to skin cancer and premature aging. Only products that pass a test can be labeled “broad spectrum.” Products that aren’t broad spectrum must carry a warning that they only protect against sunburn, not skin cancer or skin aging.
Choose a sunscreen with a sun protection factor (SPF) of 30 or higher. The SPF number is the level of protection the sunscreen provides against UVB rays. Higher SPF numbers do mean more protection, but the higher you go, the smaller the difference becomes. SPF 15 sunscreens filter out about 93% of UVB rays, while SPF 30 sunscreens filter out about 97%; SPF 50 sunscreens filter about 98%, and SPF 100 filter about 99%. No sunscreen protects you completely. The FDA requires any sunscreen with an SPF below 15 to carry a warning that it only protects against sunburn, not skin cancer or skin aging.
“Water resistant” does not mean “No sunscreens are waterproof or “sweatproof,” and manufacturers are not allowed to claim that they are. If a product’s front label makes claims of being water-resistant, it must specify whether it lasts for 40 minutes or 80 minutes while swimming or sweating. For best results, reapply sunscreen at least every 2 hours and even more often if you are swimming or sweating. Sunscreen usually rubs off when you towel yourself dry, so you will need to put more on.