A sunscreen ‘gamechanger?’ What the science says about bemotrizinol

By Adam Hadhazy

The FDA finally gave the green light to bemotrizinol. We consulted three Stanford Medicine experts about why this is considered a massive leap forward for skin health in the U.S.

Contrary to the old adage, there is something new under the sun after all — at least here in the United States. For the first time in 27 years, the U.S. Food and Drug Administration has approved a new active sunscreen ingredient for over-the-counter use.

It’s a chemical called bemotrizinol (“beh-moh-TRIZ-in-ol”), also referred to as BEMT, and it offers major advantages over presently available U.S. sunscreens, according to three Stanford Medicine dermatologists.

Here’s what these experts on skin protection and ultraviolet radiation had to say about this new product, due to hit shelves in September.

What, exactly, is bemotrizinol?

Bemotrizinol was developed by Swiss chemists seeking better sunscreens in the 1990s. (Formula C₃₈H₄₉N₃O₅ for the chemistry geeks out there.).

It’s oil-soluble, meaning bemotrizinol would absorb into our oil-rich skin except for the fact that it is a big molecule. Instead, bemotrizinol is minimally absorbed through the skin and adheres well to our bodies, forming a layer that absorbs ultraviolet light from the sun and converts it to harmless heat.

Zakia Rahman, Susan Swetter and Joyce Teng

What makes bemotrizinol different from sunscreens already available?

From the pure standpoint of protecting our skin from the sun, bemotrizinol is a “gamechanger,” said Susan Swetter, MD, the Mosbacher Professor in Dermatology co-director of the Melanoma and Cutaneous Oncology Programs at Stanford Medicine and the Stanford Cancer Institute. “It’s the best broad spectrum ultraviolet radiation filter available.”

Most sunscreens claim to offer broad spectrum coverage, meaning they absorb both kinds of ultraviolet light — dubbed UVA and UVB — that reach ground level and damage our skin. But available U.S. sunscreen filters do not cover the full spectrum of UVA, meaning a portion of this skin-penetrating light goes unchecked. “We have not had a good UVA filter on the U.S. market to date,” said Joyce Teng, MD, PhD, a professor of dermatology and director of Pediatric Dermatology at Stanford Children’s Health.

To be more specific:

Ultraviolet A (UVA) has a wavelength of 315-400 nanometers (billionths of a meter). About 95% of the ultraviolet radiation at the Earth’s surface is UVA. A lower-energy form of ultraviolet light, UVA more easily penetrates the skin and primarily causes photoaging, meaning wrinkles and sagging. Rahman notes it’s important to remember UVA is also a cause of skin cancer, as demonstrated since the late 1980s when people had higher rates of skin cancer on the driving side of their face due to UVA penetration.
Ultraviolet B (UVB) has a wavelength of 280-315 nanometers and comprises the remaining 5% of ground-level ultraviolet. Being more energetic than UVA, UVB wrecks greater amounts of havoc through the top layer of skin, primarily causing sunburn and directly damaging DNA, significantly increasing cancer risk.

Sunscreens historically available in the U.S. have provided UVA coverage only out to about 370 nanometers. Bemotrizinol covers the whole UVA spectrum, out to 400 nanometers. “Bemotrizinol is a huge step forward compared to so many other things we’ve had,” said Zakia Rahman, MD, a clinical professor of dermatology and director of the resident laser and aesthetic clinic at Stanford Medicine.

Why did it take so long for bemotrizinol to be approved in the U.S.?

Chalk it up to different regulatory structures. Unlike most of the world, which treats sunscreen as an over-the-counter cosmetic, the U.S. has historically classified sunscreen as an over-the-counter drug. Accordingly, to be sold in American stores, sunscreens must go through strict regulatory approval for safety — including human testing — as well as efficacy and clear labeling. This is so consumers can easily understand how to safely administer the product themselves.

Those extra regulatory steps, plus bureaucratic rigamarole, held up ingredient approval for more than two decades. This involved legislation such as the Sunscreen Innovation Act from 2014 to create an official regulatory pathway for bemotrizinol review, and eventually the Coronavirus Aid, Relief, and Economic Security (CARES) Act of 2020 to modernize the over-the-counter drugs regulatory framework.

“I don’t want to say ‘battle,’ but it’s certainly been a greater-than-20-year effort to get superior ultraviolet filters incorporated into our sunscreens,” Swetter said.

Should I be concerned that the FDA took so long to approve bemotrizinol?

No, quite the opposite, the Stanford Medicine experts said. “We have waited a really long time to have a new sunscreen option that’s better at UVA protection. On the plus side, there’s been added protection for consumers because of the testing process,” said Rahman, building on the safety history of bemotrizinol since its introduction in other countries circa 2000.

As part of its review, the FDA considered animal studies that showed no evidence for increased cancer risk or endocrine disruption, which is when substances interfere with natural hormonal systems, often manifesting as reproductive changes in parents or developmental issues in offspring.

Human testing of the 6% bemotrizinol concentration approved in the U.S. also found no signs of concerning skin irritation. Skin absorption, especially in pregnant women and children, was another significant concern, but testing ruled that out as well. “Since the bemotrizinol molecule is large, it does not cross the skin barrier easily, so that minimizes risk of systemic absorption,” Teng said.

Overall, the FDA approved the chemical not only for sunscreens for adults but also children as young as six months. That could prove critical for bringing down skin cancer rates in subsequent generations.

“Bemotrizinol is tried and true and its FDA approval is great news for consumers,” Swetter said.