If you put on sunscreen before leaving home and plan to spend the afternoon outside, make a plan for the next application too. The usual outdoor interval is at least every two hours, and swimming, sweating, or towel drying can mean reapplying sooner. The Drug Facts directions on your own sunscreen tell you how to handle those situations.
Start with the outdoor timing
Apply sunscreen to uncovered skin before heading outside. FDA guidance generally advises applying it 15 minutes before sun exposure. The American Academy of Dermatology recommends a broad-spectrum, water-resistant sunscreen with SPF 30 or higher. Check exposed areas you might overlook, such as your ears, the back of your neck, and the tops of your feet in sandals.
If you remain outside, reapply at least every two hours. A phone reminder can help, especially on a day when you switch between errands, a walk, and lunch outdoors. Use the amount and directions on your product. A higher SPF does not extend the interval.
Read the water-resistance number on the label
On a U.S. sunscreen label, 40 or 80 minutes tells you how long the product was tested to retain its labeled protection in water. It is the interval to follow during swimming or sweating, not the duration of every application. Sunscreen can wash off, including formulas labeled water resistant.
| Situation | What to do |
|---|---|
| Outdoors without swimming or heavy sweating | Reapply at least every two hours. |
| Swimming or sweating | Follow the water-resistant label, typically after 40 or 80 minutes of swimming or sweating. |
| Drying with a towel | Reapply immediately after towel drying, as directed on a water-resistant sunscreen label. |
| Bottle has no water-resistance claim | Use a water-resistant sunscreen if you expect to swim or sweat. |
Try it on a real outing
Say you apply before heading out at 11 a.m. and spend the afternoon in a park. Plan the next application by 1 p.m. while outdoors. If you swim or sweat enough to reach the label's shorter interval, reapply sooner. If you towel dry after swimming, apply again then. Tie the reminder to something already in your plans, such as a drink break.
Pack sun-protective clothing, a hat, and sunglasses, and look for shade. A timer makes reapplication easier, but it cannot tell you how much UV exposure you are getting.
Sources & further reading
- U.S. Food and Drug Administration: Tips to Stay Safe in the Sun ↗
- U.S. Food and Drug Administration: Sunscreen Labeling and Effectiveness Testing ↗
- American Academy of Dermatology: How to Apply Sunscreen ↗
Manufacturer information, when cited, is a commercial source. It does not establish that a finished product is clinically effective.
