You put on sunscreen like you’re supposed to, go out for an enjoyable day at the beach or the park, and then come home with a sunburn – how did that happen?
A couple of factors can result in you getting less protection from your sunscreen than you think you’ll have. The first is that the SPF rating on the tube overstates the practical protection you get by a good margin. It’s not that the manufacturers are trying to pull one over on us; we all use a good deal less than the amount used to assay a product’s SPF rating. So, if you apply a “normal” amount of SPF 30 sunscreen, you’re likely getting quite a bit less.
The second factor is that sunscreen’s active ingredients are degraded by the sun’s energy. After 90 minutes or so, you may still have the vehicle, or lotion, on your skin, but not much active sun protection. That is the reason all products recommend reapplication after a certain period of time.
So, how do you prevent sunburns? First of all, reapply your sunscreen as directed on the product. Realize that you probably aren’t getting the full SPF protection listed on the product and consider using a higher-rated product if you’re consistently getting burned.
What SPF should you use? All dermatologists have their preferences, but using products with SPF 15-30 for daily activities and 30-60 for outdoor activities would be a good place to start. Your particular circumstances may require a different recommendation – be sure to ask your dermatologist what is right for you.