1. Active ingredients. These are what absorb and/or reflect rays, as opposed to the ingredients that soothe skin or enhance the texture of the product.
- Avobenzone: A common active-chemical ingredient, it penetrates the skin’s surface and helps absorb harmful UVA rays. If avobenzone is on the label, also look for ingredients such as octocrylene and octisalate, which stabilize avobenzone so that it remains effective longer. Some sunscreens contain Helioplex, a fancy name for a technology that stabilizes avobenzone.
- Zinc oxide or titanium dioxide: These “actives” are physical compounds. Rather than absorbing rays, they reflect them away from the skin. They’re a good choice for those with sensitive skin.
2. PA rating. This Japanese rating system (which is growing in popularity in the United States) measures UVA protection on a scale of one to three pluses, but it isn’t yet approved by the Food and Drug Administration (FDA). Since there’s no easy way to know how much UVA protection you’re getting, always use a broad-spectrum sunscreen (see below).
3. Water resistance. According to the FDA, a product that’s labeled “water-resistant” maintains its SPF protection for at least 40 minutes of swimming or sweating. (Even if the label says so, experts maintain no sunscreen is 100 percent waterproof.) “Very water-resistant” or “very sweat-resistant” products protect for at least 80 minutes.
4. Broad-spectrum coverage. This term means the product protects against both types of rays: UVB and UVA. UVB rays burn skin, and UVA rays can cause age-related damage. Both kinds have been linked to skin cancer.
5. SPF. This number refers to the relative amount of protection you’re getting from UVB rays—not how much longer you can stay in the sun than you could without protection. To put it in perspective: An SPF 15 product protects skin from about 93 percent of UVB rays; an SPF 45, about 97 percent. There is no sunscreen that blocks 100 percent.
For our sunscreen recommendations, plus seasonal skin-care advice, see The Best Sunscreens (and Summer Skin-Care Tips). To find solutions for summer skin problems, see How to Treat Common Summer Skin Complaints.