Sunscreen and Sweat: The Summer Workout Problem
Keeping protection on when you're drenched.
US sunscreens may claim 'water resistant' for only 40 or 80 minutes — verified by testing after immersion — and the FDA bans the terms 'waterproof' and 'sweatproof' as misleading.
Dermatologists stress that no sunscreen is truly sweatproof; once you've been sweating heavily for 40 to 80 minutes, the water-resistance window has lapsed and you need to reapply.
Questions we get a lot
Does sweat wash sunscreen off?
Yes — heavy sweating and the rubbing that comes with it gradually remove sunscreen, cutting its protection. 'Water-resistant' products hold up for only 40 or 80 minutes of sweating or swimming, so reapply once that window passes, and choose a water-resistant broad-spectrum SPF 30+ for workouts.
What does 'water resistant' actually mean on sunscreen?
In the US, sunscreen can be labeled 'water resistant' for 40 or 80 minutes, based on testing after water immersion — there is no such thing as 'waterproof' or 'sweatproof.' For a sweaty summer workout, reapply after that rated time or every two hours, whichever comes first.
When is the UV index high enough to need sun protection during exercise?
Dermatologists recommend sun protection whenever the UV Index is 3 or higher, which covers most summer daytime hours. For outdoor workouts, use a water-resistant broad-spectrum SPF 30+, a hat or visor, and reapply regularly since sweat steadily wears it away.
r/running: 'What sunscreen actually stays on when I'm sweating buckets on a summer run?'