Sunscreen, what you need to know.

The fact that we all have to wear sunscreen is a no-brainer. But beyond that, we have to start making decisions about what type of sunscreen to wear and when. And there’s no one right answer: the best sunscreen for you will depend on a number of factors, including formulation, skin type and level of sun exposure.

If you’re like most of us, you sometimes struggle with translating sunscreen labels. Don’t worry: you don’t need to get an advanced degree in sunscreen terminology. We’ll explain the most common sunscreen terms and what they mean for you—so you can spend more time enjoying the sun and less time researching how to protect yourself from it.

UV radiation

Ultraviolet radiation (UV) is the reason we need to wear sunscreen. UV is emitted by the sun but, unlike visible light, it cannot be seen by the human eye. Despite that, UV is incredibly powerful and can be harmful to humans. There are two main types of UV you need to know about:

• UVA. Even though you won’t see immediate signs of it, UVA penetrates into deeper levels of the skin and can contribute over time to premature skin aging and wrinkles as well as melanoma. UVA rays can penetrate both clouds and glass.
• UVB. Rays of UVB affect the outer layer of skin and are primarily what cause sunburns; they can also contribute to premature aging and the development of a common type of skin cancer, called melanoma. UVB is strongest from 10 a.m. to 4 p.m., and can partially penetrate clouds but not glass.

What this means for you: Choose sunscreen labeled “broad spectrum,” which offers protection from both UVB and UVA. When going outdoors, wear sunscreen even during winter and on cloudy days. One exception: don’t put sunscreen on children under six months of age; shield them from the sun by keeping them in the shade and covered with protective clothing, including a hat.

Sunscreen SPF levels

Sun Protection Factor (SPF) is a number from 2 to 50+ that tells you the percentage of UVB a sunscreen can block and how long your sunscreen will protect you from the sun:

• SPF 15 blocks 93% of UVB
• SPF 30 blocks 97% of UVB
• SPF 50 blocks 98% of UVB

Sunscreen lower than SPF 15 helps prevent only sunburn and no sunscreen can block 100 percent of UVB. And while broad spectrum sunscreen blocks some amount of UVA, there is no standard measure for UVA protection, which is why SPF indicates only UVB protection.

What this means for you: In general, the fairer your skin, the stronger the UVB and the longer you’re in the sun, the higher you should go on SPF. But you must always re-apply; SPF 30 blocks 4 percent more UVB rays than SPF 15, but that doesn’t mean SPF 30 allows you to safely stay in the sun twice as long.

Sunscreen features

Beyond UV protection, some products offer additional features. Many of the terms used to describe these features are regulated by the U.S. Food and Drug Administration (FDA). Some of the most common sunscreen terms you’ll see include:

• Broad spectrum sunscreen. The FDA allows a product to be labeled “broad spectrum” if it passes a test proving that it offers protection from a percentage of both UVB and UVA radiation. The percentage of UVB that is blocked depends on the SPF level.
• Continuous sunscreen. This term appears on some products and can be somewhat misleading, since no sunscreen can provide protection for more than two hours without re-application. There is no FDA regulation of this term.
• Hypoallergenic sunscreen. This term is meant to suggest that the sunscreen is less likely to cause allergic reactions, which would be a good thing, especially for people with sensitive skin. But the FDA has no definition of the term “hypoallergenic,” so companies can label products with that term without having to prove they meet any hypoallergenic standards.
• Non-comedogenic sunscreen. The FDA provides loose guidelines for this term. It means the product does not contain ingredients known to clog pores, which is important if you have acne-prone skin. However, there is no independent organization responsible for verifying claims that products are non-comedogenic. Many non-comedogenic sunscreens are oil-free.
• Sweat-resistant and water-resistant sunscreen. The FDA has approved these two terms to apply to either 40- or 80-minute increments. Sunscreens are no longer allowed to be labeled as “sweat-proof” or “water-proof.”

What this means for you: If you’re neither sweating nor in water, re-apply sunscreen every two hours. If you are sweating or in the water, re-apply every 40 or 80 minutes, depending on the label instructions.

Sunscreen ingredients

The list of common sunscreen ingredients is long. The main thing to keep in mind is the two different ways a sunscreen can provide UV protection: chemical or mineral.

• Chemical absorber sunscreens. These sunscreens contain carbon-based compounds made in labs. When UV rays hit the skin, the chemicals absorb the UV so it can’t reach the skin, then release it as harmless energy. Look for “oxybenzone,” “avobenzone,” “octisalate,” “octocrylene,” “homosalate” or “octinoxate” in the ingredients list.
• Mineral sunscreens. These sunscreens rely on either natural zinc oxide or titanium dioxide to create a physical barrier that reflects UV away from the skin; for this reason, they’re also called “physical sunscreen.” Look for “zinc” or “mineral” in the product name or “zinc oxide” or “titanium dioxide” in the ingredients list.

What this means for you: Scientific research on both types of sunscreen is constantly under way and there is a lot of information out there, much of which is conflicting and very little of it is decisive. But there’s wide agreement within the medical community that wearing any kind of sunscreen regularly is better than none at all.

• Chemical sunscreens are more common, so there’s more selection in terms of formulation (lotion, spray or stick) and they’re less likely to leave a sticky film on the skin. Some people have concerns about chemical sunscreens being absorbed by the skin and potentially causing hormonal changes in the body. Right now there is no scientific evidence that chemical sunscreens directly harm humans, though there is evidence that some common ingredients in chemical sunscreens can disrupt hormone function. If you have any concerns about chemical exposure, mineral sunscreen might be the best route for you.
• Mineral sunscreens are minimally absorbed, though some people are concerned about the safety of the nanoparticle technology used in mineral sunscreen; scientific research has yet to prove that nanoparticles pose any danger to humans. From a practical perspective, this kind of sunscreen can leave a chalky white color to the skin, especially on darker skin tones.

You’ve got sunscreen terms down now; but that doesn’t necessarily narrow your choices when it comes time to gear up for sun protection. Read How to choose the right sunscreen to find out which ones are best for a variety of needs and situations.