SCCS/1686/25: Thiomersal and Phenylmercuric Salts in Eye Cosmetics Assessed as Not Safe

The Scientific Committee on Consumer Safety (SCCS) adopted its scientific opinion on thiomersal and phenylmercuric salts on 2 February 2026. The result: both substance groups are considered not safe as preservatives in eye cosmetics at the currently permitted concentrations. The opinion is numbered SCCS/1686/25 and was published on 10 February 2026.

What it is about

Thiomersal is a mercury-containing compound (CAS number 54-64-8, EC number 200-210-4). Phenylmercuric salts are also mercury compounds. Both are used as preservatives, meaning substances that inhibit the growth of microorganisms in the product. The use case at the focus of this opinion is eye products.

The European Commission had asked the SCCS for an assessment. Specifically, the Committee was to answer two questions: First, whether there are specific concerns regarding the current use of thiomersal and phenylmercuric salts as preservatives in eye cosmetics. Second, whether this use poses a potential risk to human health.

The result of the assessment

The SCCS arrives at a clear conclusion. It relies on the so-called Margin of Safety (MoS), the safety margin. This value relates the dose at which no adverse effect is yet observed to the actual expected exposure. As a rule of thumb, an MoS of at least 100 is considered necessary to assume a sufficient safety margin.

For thiomersal and phenylmercuric salts, the MoS based on renal toxicity (kidney toxicity) as the most sensitive endpoint is below 100. In addition, the data situation on genotoxicity, meaning the potential to damage genetic material, remains unresolved. For these two reasons, the SCCS assesses the use of both substance groups as preservatives in eye cosmetics at the currently permitted concentrations as not safe.

Regarding the second question, the Committee notes that the potential risk to human health is exacerbated by additional exposure to mercury compounds from sources other than cosmetics. Consumers therefore do not absorb mercury solely through cosmetic products, which increases the overall burden.

Who the opinion affects

Affected are manufacturers and distributors who use thiomersal or phenylmercuric salts as preservatives in eye products. This includes, for example, products for the eye area where preservation is required.

Important to note: an SCCS opinion is a scientific assessment, not law. It regularly forms the technical basis for subsequent amendments to the Cosmetics Regulation (EC) No 1223/2009 by the European Commission. Whether and when the Commission will issue a regulation based on SCCS/1686/25, and what transitional periods would apply, is not evident from the available source material. Once a corresponding legal act is in place, the specific obligations will follow from it.

What manufacturers should check now

Even without an adopted regulation, the opinion provides a clear technical signal. Manufacturers can keep the following points in mind:

• Formulation screening: Check whether thiomersal (CAS 54-64-8) or phenylmercuric salts are contained in the preservation of eye products.
• Prepare alternatives: Since the SCCS classifies the current concentrations as not safe, it may be advisable to consider alternative preservation concepts at an early stage.
• Monitor legal developments: Track the Commission's further steps and possible amendments to the annexes of the Cosmetics Regulation.
• Keep documentation up to date: The safety assessment under Annex I (CPSR, Cosmetic Product Safety Report) and the Product Information File (PIF) should reflect the current scientific status.

How we support you

Formulation changes regularly entail further steps: a new or updated safety assessment, an adapted INCI declaration and, where applicable, renewed notification in the CPNP (Cosmetic Products Notification Portal). At REGULARUS, we prepare the CPSR assessment under Annex I and maintain the Product Information File. In the event of formulation or legal changes, we support the necessary adjustments. A qualified safety assessor reviews and signs the documents.

The full opinion SCCS/1686/25 is available from the European Commission (SCCS Scientific Advice on thiomersal and phenylmercuric salts). An overview of all SCCS opinions is also available online. If you would like to have your eye cosmetics reviewed in light of this assessment, please contact us via the inquiry page.