Homosalate is an organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 used in some sunscreen

Sunscreen

Sunblock is a lotion, spray, gel or other topical product that absorbs or reflects some of the sun's ultraviolet radiation on the skin exposed to sunlight and thus helps protect against sunburn...

s. It is an ester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

 formed from salicylic acid

Salicylic acid

Salicylic acid is a monohydroxybenzoic acid, a type of phenolic acid and a beta hydroxy acid. This colorless crystalline organic acid is widely used in organic synthesis and functions as a plant hormone. It is derived from the metabolism of salicin...

 and 3,3,5-trimethylcyclohexanol, a derivative of cyclohexanol

Cyclohexanol

Cyclohexanol is the organic compound with the formula 5CHOH. The molecule is related to cyclohexane ring by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid, which, when very pure, melts near room temperature...

.

The salicylic acid portion of the molecule absorbs ultraviolet

Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 rays with a wavelength from 295 nm to 315 nm, protecting the skin from sun damage. The hydrophobic cyclohexanol portion provides greasiness that prevents it from dissolving in water.

Toxicity

Contained in 45% of US Sunscreens, It has limited skin penetration in vivo <1% (Was not detected in European mothers' milk (Sarveiya V, Risk S, Benson HAE. 2004. Liquid chromatographic assay for common sunscreen agents: application to in vivo assessment of skin penetration and systemic absorption in human volunteers. Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences. 803, (2), 225-231.) Limited evidence of hormone disruption.8, 19, 22, 28. Toxic metabolites 34 (Schreurs R, Sonneveld E, Jansen JHJ, Seinen W, van der Burg B. 2005. Interaction of polycyclic musks and UV filters with the estrogen receptor (ER), androgen receptor (AR), and progesterone receptor (PR) in reporter gene bioassays. Toxicological Sciences. 83, (2), 264-272., Wolff MS, Engel SM, Berkowitz GS, Ye X, Silva MJ, Zhu C, et al. 2008. Prenatal phenol and phthalate exposures and birth outcomes. Environmental health perspectives 116(8): 1092., et al.)