It’s not breaking news that you need to be wearing SPF to protect your skin. But shopping for it can be so confusing! From all the different types—physical, chemical, spray, stick, lotion—to the various brands, how do you know if you’re choosing the right one for you and your family?
We asked Kachiu Lee, MD, a dermatologist and assistant professor of dermatology at Brown University, to shed some light on SPF so you’re not spending hours in the sunscreen aisle. Let’s start with the basics:
What is SPF?
SPF stands for sun protection factor. Basically, it measures how well a sunscreen filters your skin from UVB rays, which are the rays that give you a sunburn.
How does it work, though? An SPF amount indicates how long it will take UVB rays to burn the skin versus how long it would take someone without SPF. Example: Someone using an SPF of 30 will take 30 times as long to get burned as someone using none. (According to the American Academy of Dermatologists, an SPF of 30 will block 97 percent of the sun’s rays and last about 10 hours.)
What people don’t realize is that some SPF products do not specifically filter UVA rays.
UVA rays (or Ultra Violet A) are also a concern: UVA rays don’t cause sunburn, but they do penetrate deeper. “Ultimately, we want to protect against skin cancer, which is UVA-related,” says Lee. In fact, UVA rays are 30 to 50 time more common than UVB rays, and they can penetrate glass and clouds (sneaky!).
Choosing an SPF
In short, you’ll need SPF protection from both UVB and UVA rays. “’Broad spectrum’ SPFs protect against both UVA and UVB, which gives you a more intense protection from the sun as a whole,” says Lee. If it doesn’t say ‘broad spectrum,’ it doesn’t protect against both UVA and UVB.
There are two main types of sunscreens: physical and chemical. A physical sunscreen contains an ingredient that protects against both UVA and UVB rays (usually zinc oxide) or physically blocks the sun’s rays (like titanium dioxide). They’re often thick and go on pretty white. There are plenty of organic and more natural sunscreens (like Badger’s Broad Spectrum Zinc Oxide for Kids) of the physical kind.
Related: What 9 The Vitamin Shoppe Health Enthusiasts Always Pack In Their Beach Bags
Chemical sunscreens use ingredients that actually absorb the rays, keeping them from your skin. They’re usually thinner, spread over the skin more easily, but require more time before they begin to work. Lee says both kinds of sunscreens are effective.
What SPF factor should you get, though? Lee advises that everyone should aim to buy a broad-spectrum sunscreen with at least an SPF of 30. This recommendation is in line with what the American Academy of Dermatologists suggests.
Above that number, however, there’s not much difference in how much protection you get. Yep— that means that your SPF 50, 85, or 100 doesn’t actually provide significantly more protection (maybe three percent, if at all) than what’s in the SPF 30 tube, according to Lee.
Related: 7 Beach Activities That Double As Great Workouts
In terms of the texture of your sunscreen, Lee says that lotion sunscreens tend to provide better coverage than sprays. And sprays come with an inhalation risk, so you should always apply them outside and try to avoid breathing in any residue.
If you’re wondering if it’s worth it to buy a special sunscreen just for your face, the answer is yes, especially if you have sensitive skin, acne, or rosacea. Sunscreens for the face, like Goddess Garden Facial Natural Sunscreen, are specially-formulated not to clog pores or irritate your facial skin.
Using an SPF
When applying SPF, you need to use at least an ounce for your entire body—about the size of a shot glass (pop one in your beach bag so you always have an idea of how much to use). And although most of the labels say you should apply every four hours, Lee says every two hours is probably a better estimate for the majority of people.
If you’re applying your SPF correctly, you should actually go through a three-four ounce bottle quickly: “Most people are not using enough sunscreen,” says Lee. “You should be using way more than you think, and if you’re going to be out at the pool for a little more than half the day, you should be going through an entire bottle.”
Related: Shop broad spectrum SPFs to protect your skin from sun damage.
She also advises reapplying your SPF every time you get out of the ocean or pool. Yes, that’s even if your sunscreen says it’s “waterproof.” This is because sunscreen is actually water resistant, rather than waterproof, so you do lose protection every time you get wet. If you’ve been sweating a lot, that’s another reason to reapply.
And don’t forget to protect your lips, too—while you can use regular sunscreen in a pinch, lip balm sunscreens work best.
For a quickie reference guide, here are three steps to protecting your skin next time you head outdoors: