A while back, we posted a Linkedin poll asking you this question! Want to know what beauty experts and dermatologists think? General consensus: You should reapply sunscreen every two hours. This is because, after 2 hours, your sunscreen’s SPF value is less effective, and it loses its ability to protect your skin. Reapplying sunscreen every 2 hours ensures that you aren’t at risk of skin damage, sunburns, skin cancer, and premature aging. However, if you’re swimming or sweating, you may need to touch up your sunscreen more often.