Two JAMA studies cited by the report, for instance, found that various UV filters — the chemicals in sunscreens that absorb or block sunlight — could be detected in people’s blood after repeated application, but neither study showed effects on the body, Friedman said.

David Andrews, PhD, the EWG’s acting chief science officer, said the sunscreen ratings were based on a “comprehensive review of the most current, peer-reviewed” science plus data from federal agencies like the FDA and health and safety organizations from around the world.

“We assess ingredients for both health hazards — such as hormone disruption, developmental toxicity, and allergic reactions — and for their efficacy in protecting against UVA and UVB radiation,” said Andrews, noting that the group’s standards “go beyond what is required by [the] FDA.”

First, What Is SPF?

SPF, or sun protection factor, is the level of protection from UVB rays that a product provides.

The sun releases a full spectrum of ultraviolet (UV) radiation, a form of energy that’s part of the electromagnetic spectrum. UVB is a type of UV radiation, and so is UVA. UVB rays are shorter and have a greater effect on sunburn. They can also damage the skin’s DNA, leading to skin cancer.

SPF 15 provides over 94% protection, allowing about 6% of UVB rays to reach your skin. SPF 30 provides 97% protection, SPF 50 provides 98% protection, and SPF 100 provides 99% protection. The SPF number indicates protection compared to no sunscreen. For instance, it will take 30 times longer for your skin to burn if you wear the recommended amount of SPF 30, versus wearing no sunscreen.

What About UVA?

UVA rays are longer and penetrate deeper into the skin, causing skin aging. They also contribute to sunburn, skin cancers, and rashes, said Zakia Rahman, MD, clinical professor of dermatology at Stanford.

Broad-spectrum sunscreens protect you against both UVB and — to an extent — UVA rays.

However, “they’re not great at UVA,” Friedman said. “They’re sufficient from an FDA perspective, but they’re not great. We have very few UVA filters.”

What’s the Difference Between Mineral and Chemical Sunscreens?

“They work in different ways, but they still achieve the same effect,” said Syril Keena Que, MD, MPH, professor of dermatology at the Indiana University School of Medicine in Indianapolis.

Chemical sunscreens contain organic (carbon-containing) UV filters called oxybenzone or avobenzone, which absorb UV radiation, converting it into heat, said Que. Mineral (also known as physical) sunscreens contain UV filters like titanium dioxide or zinc oxide — metal particles that block, reflect, and scatter UV rays.

Mineral sunscreens tend to cause fewer allergic reactions and may be better for people with sensitive skin, Que said, such as babies and young children and those with skin conditions like eczema or psoriasis.

Hybrid sunscreens use both kinds of filters. When chemical filters absorb UV radiation, their electrons become excited. As they return to normal, they release that energy as heat. But over time, “they get stuck in that higher level of excitement,” Friedman said, and stop protecting your skin. Combining them with mineral filters takes some of the load off them, Friedman said. “Minerals can do it all day. They’re not going to burn out.”

Are Sunscreen Ingredients Safe?

Several sunscreen ingredients — including oxybenzone and avobenzone — lack enough safety data to be generally recognized as safe and effective (GRASE) by the FDA. Some studies in mice have linked those ingredients to cancer and hormone disruption. That has influenced the EWG’s methodology and the results of their latest sunscreen report.

“Our top recommended sunscreens are primarily mineral sunscreens using zinc oxide or titanium dioxide,” said Andrews, of the EWG. In 2019, the FDA determined that these two mineral blockers are the only sunscreen active ingredients that are GRASE.

But the GRASE category “is almost to the detriment” of consumers, Rahman said, “because a lot of chemical sunscreens work really well.” While endocrine disruption, specifically caused by microplastics, is a “legitimate” concern, “we have to balance that with skin cancer risks.”

While it’s true chemical filters lack enough research to confirm they’re safe, there’s not enough data to say they’re dangerous, either. Friedman pointed to a 2025 study that found six common chemical UV filters, including avobenzone, do not cause cancer.

So Why Not Just Use Mineral Sunscreens?

While chemical sunscreens are made so your skin absorbs them, mineral sunscreens sit on top of your skin. Both zinc oxide and titanium dioxide are “very white, so that limits who can use the products,” Rahman said. They can leave a visible white or gray layer, making them less appealing for people of color.

Some brands add tinting agents like iron oxide or pigment particles, providing protection against visible light (known to stimulate melanin production), Rahman said. That makes them potentially a good option for those who are prone to pigmentation and dark spots. But even tinted mineral sunscreens can still leave a cast on the skin.

“Being a person of color myself and having a lot of patients with pigmentary disorders, it’s important for me to talk about the different wavelengths of light and how people can protect themselves,” Rahman said.

Europe and Asia offer a wider variety of sunscreens for different skin tones, Rahman said, but because European and Asian sunscreens are regulated under a different system (one that classifies them as cosmetics, not drugs), they aren’t subject to the same rigorous testing required in the U.S., where sunscreens are regulated by the FDA as over-the-counter drugs. In 2006, the FDA granted approval to products containing Mexoryl SX, an organic compound that protects against UVA and was already being used abroad. But many dermatologists say that consumers need more options.

“We’re really advocating for the FDA to approve more products so we have new things available that cover UVA and provide a more broad-spectrum sunscreen in the U.S.,” Rahman said.

How Is SPF measured?

SPF is measured in a lab with human participants, who are doused with the recommended sunscreen amount: 2 milligrams per square centimeter of skin, or about a teaspoon for the face and an ounce (about equal to a shot glass) for the body. They’re exposed to UVB light, with and without sunscreen. SPF is determined by how long it takes for the skin to turn red.

“They look at what’s called the minimal erythema dose, which tells you how your skin responds and if it’s sunburned,” Rahman said.

Broad spectrum sunscreens also undergo lab testing using a skin-like substance instead of real skin to determine protection from UVA rays. A spectrophotometer machine helps identify different wavelengths of light and which ones are blocked, Rahman said.

Does Lab Testing Reflect How People Really Use SPF?

Not really. Most people use between 20% and 50% of the recommended amount.

“When you’re using an SPF 50, for example, it may be only equivalent to an SPF 15 or 25, based on how much you’re applying,” Que said.

The FDA outlawed use of the terms “sunblock,” “waterproof,” and “sweatproof” in 2011 because they may give people a false sense of protection from harmful rays.

What’s the Bottom Line?

Choose products that are SPF 30 or higher, broad spectrum, and water resistant for 80 minutes, Friedman said. Patch-testing samples of different sunscreens can be helpful for finding one that you like.

“The best sunscreen is the one that you’re going to use repeatedly,” Friedman said.

Que emphasized the importance of daily sunscreen use — at least SPF 30 — on the face, neck, and any exposed areas, such as arms and hands. “Oftentimes, it’s that cumulative sun damage over many years that results in skin cancer,” she said.

Use sunscreen sprays in well-ventilated areas to avoid breathing in harmful chemicals, Que said. Spray products may contain benzenes, which are carcinogens. Because benzene isn’t added to sunscreen intentionally but can result from the manufacturing process, it’s not listed on the label.

“There’s no way for consumers to identify which sprays might contain trace benzene,” Que said. “That’s why using sprays in well-ventilated areas and avoiding inhalation is wise.”

Choosing lotion-based sunscreens can reduce that risk, she said.