The Scientific Committee on Consumer Safety (SCCS) is finalising its scientific opinion on the safety of Thiomersal (CAS No. 54-64-8, EC No. 200-210-4) and Phenylmercuric salts as preservatives in cosmetic products, marking a potentially significant regulatory development under the EU Cosmetics Regulation (EC) No. 1223/2009.
The assessment (SCCS/1686/25), requested by the European Commission, was initiated in response to updated scientific data and ongoing concerns regarding mercury-based compounds. Although mercury and its derivatives are generally prohibited in cosmetics, Thiomersal and Phenylmercuric salts remain allowed as preservatives in eye products under strict concentration limits (up to 0.007% expressed as mercury).
A preliminary opinion was published on 19 November 2025 and opened for public consultation until 21 January 2026, allowing stakeholders to submit comments and additional data. Following this process, the SCCS adopted its final opinion on 2 February 2026, confirming key safety concerns.
The Committee concluded that the use of Thiomersal and Phenylmercuric salts in cosmetic eye products cannot be considered safe at the currently permitted levels. This conclusion is primarily based on a Margin of Safety (MoS) below 100 when considering renal toxicity as the most sensitive endpoint. Additionally, unresolved genotoxicity concerns further contribute to the negative safety assessment.
The SCCS also highlighted that the overall risk may be exacerbated by cumulative exposure to mercury from non-cosmetic sources, reinforcing the need for a precautionary approach.
This opinion is particularly relevant for the cosmetics industry, as it is expected to trigger regulatory follow-up actions by the European Commission, potentially leading to an amendment of Annex V of Regulation (EC) No. 1223/2009. Such a revision could restrict or fully prohibit the use of these substances as preservatives in eye products.
Overall, the finalisation of the SCCS opinion represents a critical step in the EU risk assessment process, signalling a likely tightening of rules on mercury-based preservatives and reinforcing the EU’s commitment to a high level of consumer safety.
