For the first time since the late 1990s, the US Food and Drug Administration has added another chemical, bemotrizinol or BEMT, to its list of approved active ingredients in over-the-counter sunscreens.
During heat waves, such as the ones blanketing Europe and the US, sunburns are especially dangerous because they impair sweating, increasing risks of heat exhaustion and heatstroke, the US National Weather Service warns.
Here is what you need to know about sunscreens in general and BEMT in particular:
How do sunscreen work?
The two major types of sunscreens — chemical and mineral — handle the sun’s ultraviolet rays differently.
Chemical sunscreens, including BEMT, absorb the sun’s UV rays and change their structure, converting them into heat before they can penetrate the skin. Ultimately, the chemicals themselves are absorbed into the bloodstream. Health officials say more research is needed to understand the safety impacts of long-term use.
Mineral sunscreens contain zinc oxide or titanium dioxide. They are considered safer than chemical sunscreens because they do not get absorbed into the blood. Instead, they remain on the skin, creating a barrier that reflects UV light. Older formulations often had a white appearance, but modern versions blend into skin more effectively.
What’s different about BEMT?
BEMT, which has been used in chemical sunscreens for decades in Europe, Asia and Australia, is “broad spectrum,” filtering both UVA and UVB rays simultaneously. Some chemical sun filters primarily absorb UVA rays, which lead to wrinkles, sun spots, and other signs of ageing, while other chemicals address UVB rays, which cause sunburn. Many commercial sunscreens employ multiple chemicals that also make them broad-spectrum products.
BEMT molecules are relatively large, so less of it is absorbed through the skin, said Dr Henry Lim, of Henry Ford Health in Detroit and a past president of the American Academy of Dermatology.
BEMT is also more “photo-stable” than other chemical filters, meaning it breaks down more slowly when exposed to sunlight.
BEMT is the first chemical sunscreen to be designated by the FDA as safe and effective in children as young as 6 months old.
Is BEMT available in US?
The FDA approval order takes effect in August 2026, so BEMT sunscreens won’t be on US store shelves before then.
New products for the US market are likely to combine BEMT with current sunscreen ingredients, such as zinc oxide, to increase overall effectiveness and cosmetic acceptability, said AAD President Dr Murad Alam, vice-chair of the dermatology department at Northwestern University Feinberg School of Medicine in Chicago.
Until early 2028, the Swiss-Dutch company DSM-Firmenich AG has exclusive rights to sell its BEMT formulation to US sunscreen manufacturers. The chemical will appear on ingredient lists as Parsol Shield.
BEMT is also sold outside the US as Tinosorb S by BASF.
How do US sunscreens compare to products sold elsewhere?
Even with approval of BEMT, “the United States still lags behind many other countries that have nearly twice as many approved sunscreen ingredients,” the AAD said in a statement.
Some sunscreens available outside the US are more stable, large non-absorbable molecules, good at filtering UVA and UVB, and more cosmetically elegant, and hence more likely to be used, Alam said.
While the US regulates sunscreens as over-the-counter drugs, other countries regulate them as cosmetics, a lower bar, he noted.
“Products in other countries may be more effective, but not necessarily safer,” Alam said.
“FDA does a good job being very careful about safety, although some of the newer filters, like BEMT, which are just now getting approved in the US, may be less likely to be absorbed, which is a potential safety benefit,” he said.
Does sunscreen type make a difference?
According to the AAD on its website, the best type of sunscreen is the one you will use again and again.
The group recommends use of any water-resistant sunscreen product with a Sun Protection Factor (SPF) of 30 or higher that offers broad-spectrum protection against UVA and UVB.
But when temperatures climb to 90 degrees Fahrenheit (32 degrees Celsius), with high humidity, mineral sunscreens may be preferable, some experts say.
“Mineral UV filters such as zinc oxide and titanium dioxide are inherently very stable and maintain their UV-filtering properties well, even under high heat,” said Dr. Jacqueline Watchmaker, a dermatologist in Scottsdale, Arizona.
“However, both mineral and chemical sunscreen products can be affected by prolonged exposure to excessive heat because the overall formulation – not just the active ingredients – may degrade,” she explained.
Extreme heat also means more sweating, and sweat can contribute to itchiness and rashes some people experience from ingredients in chemical sunscreens. Even in cooler weather, people with sensitive skin should opt for mineral sunscreens, the AAD advises.
Apply more sunscreen, more often
Sunscreen should be applied to dry skin 15 minutes before going outdoors and then re-applied at least every two hours, and after swimming or sweating, the AAD says.
Many individuals don’t apply enough sunscreen to achieve the level of SPF protection on the label, AAD also notes.
“Most adults need about a shot glass worth of sunscreen to cover their body,” Watchmaker said. “For high-exposure areas like the face, chest, and shoulders, I like the ‘double-layer’ trick, which involves applying one layer, letting it settle for a moment, then applying a second layer to make sure you’re getting adequate coverage.”
Keep sunscreen containers out of heat
Eight hours of exposure to temperatures above 85 F (30 C) can irreversibly alter a chemical sunscreen’s physical characteristics, resulting in decreased efficacy, research has found.
Sunscreen may have been exposed to extreme heat if its components have started to separate. If sunscreen must be left in hot vehicles or in the sun, pack it in a cooler. In addition, use caution when ordering sunscreen online in the summer because of the potential for degradation if left in a hot area or mailbox.
