Can you apply sunscreen once a day?

Why doesn't one application last all day?

Sunscreen breaks down during sun exposure, and water, sweat, towel drying and rubbing can remove it. Reapplication replaces that protection. Even a sunscreen described as offering "all day protection" still needs reapplying every two hours outdoors.23

A higher SPF does not buy you a longer interval between applications. SPF measures protection against the amount of ultraviolet radiation that causes sunburn, not the number of hours you can stay outside. SPF 50 is not permission to leave the bottle at home.4

What if you are mostly indoors?

The every two hours rule applies when you are outdoors; it is not an automatic desk alarm for every indoor situation. But being inside does not always remove exposure: UVA rays reach your skin while driving or sitting near a window. Wear SPF 30 or higher daily, and do not count on an early morning application to cover a later outdoor outing.15

Clouds and winter weather do not remove the need for protection outside. Even a short walk exposes skin to ultraviolet rays. For a brief outing, apply sunscreen beforehand; if you stay outside, continue with the reapplication schedule rather than treating the first coat as permanent.16

How to apply and reapply sunscreen

Read the application directions on your sunscreen, even if the front of the bottle has already delivered its keynote speech. Directions can differ between lotions, sticks and sprays.4

1. 1Choose SPF 30 or higher with broad spectrum protection against UVA and UVB rays, and water resistance.
2. 2Apply generously 15 minutes before going outdoors. If you plan prolonged sun exposure, UK advice is to apply 30 minutes beforehand and again just before leaving.
3. 3Cover all exposed skin. Most adults need at least one ounce to cover skin not covered by clothing; for the face, use at least one teaspoon and rub it in thoroughly.
4. 4Include the neck, ears, hands, tops of feet and exposed scalp. Protect lips with an SPF 30 lip balm.
5. 5Reapply generously every two hours outdoors. Reapply sooner after swimming, sweating, towel drying or rubbing the sunscreen off.

Does water resistant sunscreen last longer?

Water resistant does not mean waterproof. Labels specify either 40 or 80 minutes of tested protection while swimming or sweating. Follow that limit, and reapply straight after leaving the water and towel drying. Do not wait for the usual two hour interval after those activities.34

Use shade, protective clothing, a hat and sunglasses alongside sunscreen. Sunscreen cannot block every ultraviolet ray, and wearing it is not a reason to spend longer in the sun. Check the expiry date too: expired sunscreen loses protection. Keep the container out of excessive heat and direct sunlight.3456

Who needs extra care?

Be especially careful if you burn easily, have many moles, have a family history of skin cancer or spend long periods outdoors. If you have had actinic keratoses, patches of skin badly damaged by ultraviolet light, daily sun protection is particularly important because your risk of skin cancer is higher.36

Do not apply sunscreen to damaged or broken skin. Keep it out of your eyes, and rinse with water if it gets in them. Stop using the product and ask a doctor if a rash occurs. For babies under six months, keep them out of direct sunlight and ask a doctor before applying sunscreen.47