Homosalate is an ester formed from salicylic acid and 3,3,5-trimethylcyclohexanol, a derivative of cyclohexanol. It is a chemical sunscreen active ingredient that is used in approximately 45% of sunscreens in the United States. Chemical sunscreens protect the skin by first absorbing UV light, then transforming that light energy into some other form of energy, such as heat. This is in contrast to physical sunscreens which protect the skin by using physical UV filters to block or deflect UV light. Specifically, the salicylic acid portion of homosalate absorbs UV rays with a wavelength from 295 nm to 315 nm, protecting the skin from sun damage. The cyclohexanol portion of homosalate is hydrophobic, which means that is repels water.
While homosalate is an effective sunscreen ingredient, there are a few concerns regarding the safety of this ingredient. For instance, homosalate is a potential endocrine disruptor, which means that it may impact certain hormones in the body. Additionally, homosalate may enhance the absorption of pesticides in the body. Lastly, there is evidence that sunlight breaks down homosalate and other UV filters into harmful byproducts.