Do You Really Need to Reapply Sunscreen That Often?
After spending some time in the sun, you should reapply sunscreen – every two hours, as recommended by the FDA . But what if you haven’t been in the sun all this time? What if you use a mineral sunscreen that doesn’t “wear out” like some chemical sunscreens? It turns out that you still need to reapply.
As chemist Michelle Wong explains , repeated applications aren’t just about sunscreens getting used up, although some older sunscreen ingredients do become less effective, the more sunlight they are absorbed. (Today, however, many chemical sunscreens can withstand up to several hours of sunlight without degrading.) There are other reasons as well.
Sunscreen wears off
Sunscreen is invisible (ideally), so it can be difficult to imagine what happens if it is on your skin for several hours. As an illustrative example, think of foundation, a flesh-colored cosmetic that serves as the basis for many full-face looks. Like sunscreen, it should be applied evenly to the skin. Just like sunscreen, it does not “wear out” by exposure to the sun or air.
So what happens if you lay the foundation for a few hours? It definitely doesn’t look new because it doesn’t magically stick to your skin. Every time something touches your face, such as a hand or a tissue, it fades a little. (For another cosmetic example, imagine you suddenly have a lot less lipstick on your lips after you’ve eaten a sandwich.)
We may not touch our makeup too much, but consider applying sunscreen. It is in your hands and your hands touch everything. It is on your feet and the edges of your shorts will touch it. When you sit in a chair, bathe in the water, or wash with a towel after bathing, sunscreen can wear off.
Sunscreen thins and clumps even if not touched
Okay, so what if you’re sure nothing touched your face all day? Think about the foundation again. You still don’t expect him to look perfect by the end of the day, even if you’re very careful.
Your skin secretes oils and sweat, and you move as well. The combination of these factors allows a substance – be it cosmetics or sunscreen – to travel across the skin. You will end up applying the pieces of sunscreen (or foundation) to the small folds and folds of your skin. Where did this come from? From adjacent skin areas that are now thinner or absent, which means they are no longer adequately protected from the sun.
In the middle of a sunny day, this happens even more often, – explains Wong. “It is worse if there is a lot of sweating. The [sunscreen] layer also disintegrates and shatters into pieces when your skin moves — when you talk, eat, and yawn. ”
Sunscreen can also evaporate into the air and absorb into the skin over time, further thinning the product layer on the skin.
Yes, you need to reapply
Now that you know what happens to sunscreen if it has been on your skin for several hours, the answer should be obvious: yes, you need to reapply all types of sunscreen. Not because the sunscreen is used up, but because protection depends on an even layer of the substance on your skin.
The FDA recommends reapplying sunscreen every two hours, or “more often” if you’ve been sweating or swimming. Waterproof sunscreens are rated for 40 or 80 minutes of exposure to water (including sweat), so you can use this as a guideline for reapplication.
It’s also wise to reapply the product if you know you’ve washed it, such as wiping sweat off your face with your sleeve while jogging around the area.