Poor Cosmetic Ingredient SCCS/CIR Reviewed Sensitization Data

Thimerosal (Thiomersal)

INCI: THIMEROSAL

CAS Number
54-64-8
Function
Preservative (organomercury antimicrobial)
Safety Rating
POOR

Regulatory Status

🇪🇺 EU Status prohibited
🇺🇸 US Status permitted
US Notes Permitted in cosmetics at limited concentrations; FDA has not banned but restricts mercury-containing ingredients to eye-area cosmetics at ≤65 ppm (as Hg)

For full compliance data across 55 jurisdictions, use the Substance Compliance tool.

Safety Data

Margin of Safety (MoS)
adequate
Dermal Absorption
low
Sensitization
high

Calculate MoS for your specific formulation with the MoS Calculator.

Safety Opinions

Official safety assessments from the Scientific Committee on Consumer Safety (SCCS) and Cosmetic Ingredient Review (CIR).

sccs SCCS/1686/25 2 February 2026
Verdict: unknown
Max Concentration: 0.007% in eye area

Sensitization Profile

Contact sensitization data for Thimerosal (Thiomersal) based on clinical patch test studies and IFRA standards.

Sensitization Rate
high
Allergen Class
preservative
EU Allergen Listed
no
Patch Test Positive Rate
5.0%
Cross-reactivity Group
mercury-group
Reaction Type
contact-dermatitis

Source: ESSCA; IVDK; NACDG

Expert Verdict

Renal toxicity, neurotoxicity, bioaccumulation of mercury, cumulative exposure from non-cosmetic sources (vaccines, environment), SCCS recommends reevaluating Annex V authorization; likely facing future EU ban

⚠️
Concern Level: High

Regulatory Flags

preservative eu_cosing_listed

Frequently Asked Questions

Is Thimerosal (Thiomersal) safe in cosmetics?

Renal toxicity, neurotoxicity, bioaccumulation of mercury, cumulative exposure from non-cosmetic sources (vaccines, environment), SCCS recommends reevaluating Annex V authorization; likely facing future EU ban The EU classifies Thimerosal (Thiomersal) as "prohibited". Safety rating: POOR. This ingredient has been reviewed by sccs.

Is Thimerosal (Thiomersal) allowed in the EU?

Thimerosal (Thiomersal) EU regulatory status: prohibited. This is based on EU Regulation 1223/2009 and its amendments.

What does Thimerosal (Thiomersal) do in cosmetics?

Thimerosal (Thiomersal) functions as: Preservative (organomercury antimicrobial). It is classified as a cosmetic ingredient in our database. CAS number: 54-64-8.

What is the Margin of Safety for Thimerosal (Thiomersal)?

adequate The Margin of Safety (MoS) is calculated using SCCS methodology. A MoS above 100 is generally considered safe. Use the MoS Calculator tool to calculate MoS for your specific formulation and product category.

Compliance Tools

Check Thimerosal (Thiomersal) compliance across multiple jurisdictions:

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Ingredient Decoder
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82 Allergen Checker
Check for EU declarable fragrance allergens
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Substance Compliance
Check compliance across 55 jurisdictions
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MoS Calculator
Calculate Margin of Safety using SCCS methodology
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Heavy Metal Limits
Compare limits across jurisdictions

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