How long does sunscreen last on your face?

How often should I reapply sunscreen?

Choose a broad spectrum sunscreen with SPF 30 or higher, and apply at least one teaspoon across your face. Include your ears and hairline as well as the rest of your face. Clouds do not stop UVA from reaching skin, so use sunscreen outdoors on overcast days too. No sunscreen blocks 100% of UV radiation, which makes sunblock an ambitious name, and the word has given itself a demanding job title.24

Water resistant does not mean waterproof, because two similar words apparently need separate departments. In the United States, products with a water resistant label state whether they remain effective for 40 or 80 minutes while swimming or sweating. Follow the directions on your product, and reapply sooner if water or rubbing has removed the layer.5

Does sunscreen last all day?

No. Outdoors, reapply at least every two hours at every SPF, and sooner if the layer is removed. A higher SPF offers more sunburn protection while it is on, but it does not make protection last longer. SPF measures sunburn protection, not hours outdoors; SPF 15 does not mean 15 hours in the sun, and the number is a poor stopwatch. UV exposure changes with the time of day, season and location, so sunscreen is not permission to stay outside longer than you otherwise would.145

How long before going outside should I apply sunscreen?

Apply sunscreen about 15 minutes before going outdoors so it has time to protect you. Timing advice differs by country: general directions in the United States use 15 minutes before exposure, while UK advice for prolonged sun exposure says 30 minutes before leaving and again just before going out. Waiting until you are already in the sun leaves your skin unprotected while the sunscreen absorbs.23

Do I need to reapply sunscreen if I stay indoors?

If you are indoors all day and not near a window, reapplying every four to six hours is reasonable. Most UV rays can penetrate glass, so a sunny window changes the case; use the outdoor two hour interval if you spend time beside one or go outside during the day. Sun exposure adds up even when each trip outside is brief.6