Do you need SPF 30, 50, or 100? Dermatologists answer your sunscreen questions

This article was first published Politifact

Here are the numbers that show summer is on its way. It’s the countdown to the last day of school. Forecast for 90 degree temperatures. And of course, SPF 30. Or 50? Or is it time to break SPF 100?

SPF stands for Sun Protection Factor. It sounds simple enough, but what these ubiquitous numbers actually mean can be complicated.

We asked two board-certified dermatologists to answer your questions about burning SPF.

What do the different SPF numbers actually mean?

read more: Why it’s important for everyone to wear sunscreen, even if you have dark skin

The number tells you how well the sunscreen protects your skin from ultraviolet B (UVB) rays. ultraviolet light It is the biggest cause of sunburn.

Dr. Adewole Adamson, a dermatologist and professor of internal medicine at the University of Texas at Austin, said the higher the SPF, the more of these UVB rays are blocked.

However, double the SPF doesn’t mean the sunscreen is twice as protective.

For example, a sunscreen with SPF 30 blocks about 97% of UVB rays, and SPF 50 blocks about 98%, said Dr. Marisa Gershick, a New York-based dermatologist and professor of clinical dermatology at NewYork-Presbyterian Weill Cornell Medical College.

SPF can be thought of as representing the amount of solar energy required to burn your skin with sunscreen, compared to the amount of solar energy required to burn your skin without sunscreen. According to the US Food and Drug Administration.

How much SPF is enough?

Use at least SPF 30. However, SPF 30 or above is even better.

Part of the reason is that most people don’t wear enough sunscreen, which means it’s less protective than the label advertises.

“Sunscreens with a lower SPF may feel lighter or easier to apply, but they offer less protection,” says Adamson. “The higher the number, the greater the margin of error in case of under-applications.”

What else should I pay attention to when choosing a sunscreen?

Dermatologists say buy sunscreen labeled as “broad-spectrum.” That means protection from UVA and UVB rays.

SPF only tells you how well a sunscreen blocks UVB rays, not the equally harmful ultraviolet A or UVA rays. Just like UVB rays, UVA rays has been linked to sunburn, wrinkles, and some skin cancers.

read more: Why do skiers get sunburned easily? A snow scientist explains

If you sweat or spend time in the water, you should use a sunscreen labeled “water resistant.”

“Above all, find a sunscreen that feels good on your skin. Sunscreen is only as effective as you use it,” says Adamson.

Does SPF 100 block 100% of UVB rays?

No, in fact, the F.D.A. prohibited The term “sunscreen” was coined in 2011 partly because there were no sunscreens. can Blocks all UVB rays.

Garshick says SPF 100 blocks about 99% of sunlight’s UVB rays.

It offers slightly more UVB protection than lower SPF options, but the added protection gets smaller as the number goes up. Additionally, sunscreens with higher SPF can be more expensive; UC Davis Health Reported.

Remember that sunscreen is an important condition if it is applied correctly. The increase in UVB protection from SPF 50 to SPF 100 may not be overwhelming.

clock: Why is sunscreen in the US lagging behind the rest of the world?

High SPF sunscreens can also create a false sense of security, Garshick says. “You might think that people who wear SPF 100 can stay in the sun for quite a while without having to reapply, but that’s not the case.”

Whether you’re aiming for SPF 50 or SPF 80, she says it’s important to use enough sunscreen and reapply frequently. Apply at least another coat each time. 2 hours or right rear When you get out of the pool, participate in a water activity, or do anything that makes you sweat a lot.

What else is important about sunscreen?

Adequate and repeated application of sunscreen with at least SPF 30 is important, but it’s only one part of a multi-faceted approach to protecting yourself from the sun’s harmful rays.

It is better to avoid the sun during peak hours UV rays time — 10 a.m. and 4 p.m.

Also, experts say, be sure to wear a wide-brimmed hat, sunglasses, and sun-protective clothing when you’re outdoors.