For the first time in nearly three decades, the Food and Drug Administration approved a new chemical UV filter for use in sunscreens sold in the U.S. And that has many dermatologists cheering.

"This is a very big deal," says Dr. Heather Rogers, a dermatologist in Seattle and a fellow of the American Academy of Dermatology.

The new ingredient is called bemotrizinol, and it has several advantages over the chemical sunscreen ingredients previously available in the U.S., Rogers says.

"It hits like really every box for us that we have been waiting for as dermatologists and consumers," Rogers says.

Here's what you need to know about this new ingredient and how it could lead to better sunscreens sold stateside.

1. It blocks both UVA and UVB rays

Rogers says in general, you want to use sunscreens that are broad spectrum, meaning they protect against both UVA rays – the longer wavelengths that cause premature aging and wrinkles – and UVB rays, which lead to sunburns. Both types of UV rays can cause skin cancer.

She says the sunscreens currently sold in the U.S. do an excellent job of protecting against UVB rays, but the chemical UV filters available in sunscreens in the U.S. until now aren't as good at blocking out UVA rays.

Want the latest stories on the science of healthy living? Subscribe to NPR's Health newsletter.

In general, chemical sunscreens sold in the U.S. rely on an ingredient called avobenzone to block out UVA rays, says Kelly Dobos, a cosmetic chemist who teaches at the University of Cincinnati.

But avobenzone by itself isn't photo stable, meaning its protection can start to break down rapidly when exposed to sunlight. And as avobenzone breaks down, it can release molecules that lead to skin irritation, says Alexa Friedman, a senior scientist with the nonprofit Environmental Working Group, or EWG.

By contrast, bemotrizinol offers protection against both UVA and UVB rays all on its own, and it is photo stable, so it breaks down more slowly, offering better protection, Rogers says.

"So if you go a little longer than two hours to reapply your sunscreen, there will be more protection left," Rogers says. However, she says you should still reapply sunscreen every two hours.

2. It's long been used in other countries 

Bemotrizinol has been widely used in European and Asian sunscreens for decades. But it has taken 20 years for the FDA to approve its use in this country.

That's because in the U.S., sunscreens are regulated as over-the-counter drugs rather than cosmetics, as they're classified in Europe. That means ingredients need to undergo rigorous testing for safety and efficacy before they can be approved for use in the U.S.

"It's really expensive and time consuming," Dobos says. The European company DSM-Firmenich spent at least $18 million over more than two decades in its push to gain FDA approval for bemotrizinol.

3. It has a well-documented safety profile

However, all that testing means bemotrizinol has more safety data to back it up than any other chemical sunscreen ingredient currently approved in the U.S., says Friedman of EWG.

"This ingredient is exciting because we have that data to support its safety," Friedman says.

Friedman says animal testing showed bemotrizinol doesn't lead to concerns like reproductive harm, while clinical testing on humans found that it does not irritate the skin, even after repeated application over time, "which is hopefully how people are using sunscreens."

And because bemotrizinol's molecules are larger, it's not readily absorbed by the skin and into the bloodstream, she says.

That's important, because studies have shown that some of the other chemical sunscreen UV filters sold in the U.S. can be absorbed in the bloodstream, prompting calls for more safety data and leading to a backlash against sunscreen on social media fueled by misinformation. Rogers says that trend is concerning because skin cancer is the most common form of cancer.

"We just need to have sunscreen that people will use, that they'll trust," Rogers says. "And this ingredient is going to allow that to happen. And that is very exciting."

And bemotrizinol is also considered to be non-irritating, Friedman says. That should be welcome news to people who've been put off by chemical sunscreens in the past.

4. It could lead to sunscreens that look better on you

Until now, Rogers says, the only sunscreen ingredient available in the U.S. that offered the aforementioned advantages of bemotrizinol – photo stable, non-irritating, minimally absorbed into the skin and with good broad spectrum protection against both UVA and UVB rays – was zinc oxide.

Both zinc oxide and titanium dioxide are mineral UV filters. Both chemical sunscreens and mineral sunscreens work by absorbing UV rays from the sun. Mineral sunscreens also reflect some UV rays. The bigger difference is that mineral sunscreens sit on the surface of the skin, while chemical sunscreens get absorbed into the skin, Rogers says.

The downside of mineral sunscreens is that they can leave an unattractive white cast on the skin – think of lifeguards with white paste on their noses. "Particularly if you're a person of color, zinc is going to make you look pale, white or ashy, which really makes it hard to use on a regular basis," Rogers says.

Bemotrizinol, on the other hand, is transparent on the skin, and because it protects against both UVA and UVB rays on its own, it doesn't have to be mixed with as many other chemical filters and stabilizers to achieve broad spectrum protection, Dobos adds. She says that should lead to more aesthetically pleasing, less greasy sunscreen formulations in the near future.

"I think it's a real win for public health," Dobos says. "If we can make a sunscreen that consumers like to use and want to use and apply in the proper amounts, I think that's something that's really going to be a win for consumers."

DSM-Firmenich has exclusive rights to market bemotrizinol in the U.S. for 18 months. It will be sold under the brand name Parsol Shield. The company says the first sunscreen products containing the ingredient should start hitting American store shelves around September.