You may not have heard of homosalate before. Still, if you wear sunscreen every morning (insert mandatory reminder, daily SPF is non-negotiable), there's a good chance you're using that ingredient every day without even knowing it. Sunscreens fall into two broad categories: physical formulas (which rely on minerals like zinc oxide and titanium dioxide to cling to the surface of the skin and deflect the rays) and chemical formulas (which rely on chemical ingredients to penetrate the skin and absorb UV rays before they can cause damage). Homosalate, the main active ingredient of the latter, is found in a range of chemical sunscreens.
Next, dermatologist Eddie Fincher, cosmetic chemist David Petrillo, and board-certified cosmetic dermatologist Shereene Idriss discuss everything you need to know about homosalate, including the controversy surrounding it.
"Homosalate is an organic compound that belongs to the salicylates group of chemicals," Petrillo explained. It's a chemical sunscreen that protects the skin from the sun by absorbing UV rays and converting them into heat, without causing DNA damage to skin cells, he added. There are many other chemical sunscreen ingredients, but homosalate is very common. In fact, Finch points out, it's in almost half of all commercially available sunscreens.

The mechanism of action of homosalate (and that of any chemical sunscreen) depends on it being absorbed by the skin (unlike physical sunscreens that sit on the surface of the skin). It is this absorption into the body that has sparked discussions about the safety of these ingredients.
Benefits of Homosalate for Skin

According to Petrillo, there isn't much difference between the various chemical sunscreen ingredients, and all of them work in the same way. The difference lies in which specific UV rays they can absorb and protect against.

UVB blockers: Homosalate, in particular, is a UVB blocker that protects against UV damage known to cause skin cancer, says Fincher. In that regard, "because it has very limited efficacy against UVA rays, it needs to be combined with other agents to ensure complete protection," adds Idriss. (She also notes that homosalate is not particularly photostable and needs to be combined with other ingredients to remain stable.)
Broad-spectrum sunscreen ingredients: Finch points out that it's the combination of chemical sunscreen ingredients—some of which protect against UVA rays and others that protect against UVB rays—that provide a wider range of protection, so a sunscreen can be called "broad-spectrum."