Homosalate
Also known as Homosalate, HMS, 3,3,5-trimethylcyclohexyl salicylate, homomenthyl salicylate
“EU SCCS says: restricted.”
Homosalate (CAS 118-56-9) is an organic UVB filter with documented systemic absorption after topical application. SCCS/1622/20 (Final Opinion, June 2021) concluded homosalate is not safe at the previously permitted 10% level, establishing 0.5% as the maximum safe single-product concentration based on a LOAEL of 60 mg/kg bw/d from a combined repeated dose/reproductive screening study, adjusted NOAEL of 10 mg/kg bw/d, and 5.3% dermal absorption. Endocrine disruption evidence was assessed as inconclusive and equivocal: in vitro studies indicate anti-androgenic and estrogenic activity; in vivo data showed thyroid, sperm, and hormone-level changes but under study conditions of limited reliability. The evidence base is moderate: human biomonitoring confirms systemic absorption (PMID 38485782), zebrafish/H295R studies show endocrine-active effects at environmentally relevant concentrations (PMID 37758070), and UV filter reviews note sex-hormone disruption signals (PMID 33991024).
Effective UVB filter with broad absorption in the UVB range (295-315 nm); historically used at up to 10% in sunscreens providing meaningful photoprotection
Low acute oral and dermal toxicity (LD50 > 5000 mg/kg in rats and rabbits); not a skin sensitiser; no genotoxic potential in standard GLP battery
No photo-genotoxic or photo-clastogenic potential in bacterial gene mutation and chromosomal aberration tests with and without UV irradiation
Clear, colourless to pale yellow liquid with good formulation compatibility, widely used as a solvent for other UV filters in sunscreen formulations
- · Metabolic conversion to salicylic acid in vitro; salicylic acid is itself considered an endocrine disruptor by the Danish EPA, adding combined-exposure concern not fully resolved in SCCS/1622/20
SCCS/1622/20 concluded homosalate is not safe as a UV filter at concentrations up to 10%; EU Regulation 2022/2195 subsequently restricted homosalate to face products only (excluding propellant sprays) at a maximum of 7.34% — a regulatory compromise above the SCCS science-based 0.5% limit, reflecting a phased transition
Potential endocrine disruption: SCCS/1622/20 found evidence from in vitro and in vivo studies suggesting anti-androgenic and estrogenic activity; evidence is inconclusive but could not be ruled out, preventing derivation of an endocrine-specific point of departure
Systemic absorption confirmed in humans after whole-body sunscreen application (5.3% dermal absorption in vitro; plasma detection and human milk detection in vivo); margin of safety at 10% use concentration was only 6.3 — far below the target MoS of 100
Reproductive and developmental signals in animal studies (increased post-implantation loss, thyroid hypertrophy, sperm changes) under OECD TG 422; study reliability limited by constant-lighting conditions during conduct
ECHA compliance check under REACH (March 2018) requested sub-chronic toxicity, pre-natal developmental toxicity, and extended one-generation reproductive toxicity studies — data gap not closed at time of SCCS opinion
SCCS Opinion on Homosalate (CAS No 118-56-9, EC No 204-260-8) — SCCS/1622/20, Final Opinion adopted 24-25 June 2021
“In the SCCS's opinion, the use of homosalate as a UV filter in cosmetic products is safe for the consumer up to a maximum concentration of 0.5% homosalate in the final product.”— SCCS/1622/20 Final Opinion, p. 3 (Abstract section)