How often should sunscreen be applied?

Do you need sunscreen every day?

Use sunscreen every day you will be outside, including in winter and on cloudy days. Clouds let harmful ultraviolet rays through. Apply sunscreen to skin clothing does not cover, whether you are spending the afternoon outside or heading out for everyday activities. UVA rays, which contribute to skin aging, also pass through window glass, so being behind glass does not remove all sun exposure.3

How to apply and reapply sunscreen

1. 1Choose broad spectrum SPF 30 or higher, which protects against both UVA and UVB rays. Choose water resistance if you will swim or sweat.
2. 2Apply generously to dry skin 15 minutes before going outdoors. Cover all exposed areas, including your ears, neck, hands, tops of feet, hairline and exposed scalp.
3. 3Use about one ounce, roughly a shot glass, to cover an adult's exposed skin. Larger bodies can need more. For the face, use at least one teaspoon. Protect lips with SPF 30 or higher lip balm.
4. 4Reapply generously at least every two hours outdoors. Apply sooner after water, heavy sweating, towel drying or rubbing that removes sunscreen.

If you expect to stay in the sun long enough to risk burning, apply sunscreen twice before leaving: once 30 minutes beforehand and again just before going out. Cover exposed skin thoroughly each time. Applying too thin a layer reduces protection, so frequent applications do not replace using enough.2

What changes when you swim or sweat?

Water resistant does not mean waterproof, even if the bottle looks dressed for a triathlon. Look for a tested water resistance time of 40 or 80 minutes on the label. Reapply when that time is reached during swimming or sweating, and immediately after getting out of the water or towel drying. The two hour interval applies when you remain dry; it is not permission to swim for two hours without reapplying.24

Does SPF 50 last longer than SPF 30?

No. A higher SPF gives greater protection against sunburn, not a longer reapplication interval. Reapply SPF 50 on the same outdoor schedule as SPF 30. Mineral, chemical and hybrid sunscreens all need reapplication because sunscreen can degrade, wear off or be removed. For extended outdoor exposure, such as a beach day, choose SPF 50 or higher and keep reapplying.135

What about makeup, sprays and sticks?

SPF in moisturizer or makeup does not change the outdoor reapplication schedule. Powder sunscreen can help with touch ups over makeup, but it should not be your only sunscreen, so a compact does not get to run the whole department. With a stick, slightly overlap each stroke for even coverage. With a spray, apply until skin has an even sheen, then rub it in. Spray into your hands before applying to your face, and avoid inhaling it.13

What else matters besides reapplying?

Sunscreen works alongside shade, a hat, sunglasses and protective clothing, rather than being handed the entire job by a bottle. Keep the container out of excessive heat and direct sun, and replace expired sunscreen. Keep babies under six months out of direct sunlight and ask a doctor before applying sunscreen to them.235

Do not apply sunscreen to damaged or broken skin. Stop using it and ask a doctor if a rash occurs. If you develop sunburn, stay out of the sun until the redness has gone; seek medical help if you feel unwell or your skin swells badly or blisters.26