(HealthDay)—You know you're supposed to slather on a high-SPF sunscreen before going out in the sun, but these five steps will help you double up on that protection.
First, it's important to know that there are two types of harmful ultraviolet rays. UVA rays cause lasting skin damage and aging. UVB rays cause sunburn along with skin damage. Both can lead to skin cancer, so your sunscreen should protect against both. Look for the word "broad-spectrum" on the label.
Next, you want to check out the ingredients. Sun protection products may contain chemical and/or physical sunscreens. Most products use chemical sunscreens, like oxybenzone, that absorb damaging UV rays. Zinc oxide and titanium dioxide are physical sunscreens. They sit on the skin and reflect and diffuse UV rays. They also work right away, unlike chemical sunscreens—it can take 30 minutes before they're effective. Physical sunscreens might be better for youngsters and people with sensitive skin.
Third, know your number. The SPF, or sun protection factor, measures how well the sunscreen will shield you from UVB damage. In general, SPF 15 provides a good level of protection from sunburn, skin cancer and aging. But if you are very light skinned or have had skin cancer, ask your doctor if the increased protection of SPF 30 or 50 is better for you.
How much to apply? About an ounce—two tablespoons—for head-to-toe coverage. If you're using a spray, apply it until you can see an even sheen on your skin. In general, reapply sunscreen at least every 2 hours and after swimming, sweating or toweling off. If you're going to be exercising outdoors, look for "water-resistant" sunscreen, which must specify whether it protects for 40 or 80 minutes of vigorous activity so that you know how often to reapply it.
Explore further: Sunscreen 101
The Skin Cancer Foundation has detailed information on the importance of wearing sunscreen to protect your skin.