Is Thimerosal (Thiomersal) safe in cosmetics?
Thimerosal (Thiomersal) has a safety rating of "POOR" in our database. EU status: prohibited. US status: permitted. This ingredient has been reviewed by sccs.
Thimerosal (Thiomersal)
Also known as: ((o-Carboxyphenyl)thio)ethylmercury sodium salt, Merthiolate, Mercurate(1-), ethyl[2-(mercapto-.kappa.S)benzoato(2-)-.kappa.O]-, sodium (1:1), Caswell No. 766, EINECS 200-210-4 (+15 more)
INCI: THIMEROSAL
Thimerosal (Thiomersal) (CAS 54-64-8) is a cosmetic cosmetic ingredient functioning as Preservative (organomercury antimicrobial). EU Regulation 1223/2009 status: prohibited; 1 safety opinion reviewed (sccs). Industrial safety data is also available in the chemical safety database. Same-CAS public records also appear in industrial chemical safety and pharmaceutical data.
View industrial chemical safety profile for CAS 54-64-8 →
Auto-generated CPSR Part A draft with source citations
Cross-Vertical Regulatory Divergence
Thimerosal (Thiomersal) is prohibited in EU cosmetics but has active industrial GHS classifications (H301, H317, H320, H341, H351, H360, H371, H372).
Source: Cosmetics: ingredients.eu_status; Chemicals: ghs_classifications.signal_word/hazard_statement_code
Function
Preservative (organomercury antimicrobial)
Safety Rating
POOR
Chemistry & Identifiers
IUPAC Name
sodium (2-carboxylatophenyl)sulfanyl-ethylmercury
InChIKey
RTKIYNMVFMVABJ-UHFFFAOYSA-L
Regulatory Status
EU EU Status
prohibited
US 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 multiple jurisdictions, use the Substance Compliance tool.
Safety Data
Margin of Safety, dermal absorption, and sensitization profile summaries for Thimerosal (Thiomersal).
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
EU CosIng Annex Listing
European Commission CosIng database Annex references per Regulation (EC) No 1223/2009.
Annex V — Permitted Preservatives
Product type: Eye products
Max: 0.007% (of Hg)
If mixed with other mercurial compounds authorized by this Regulation, the maximum concentration of Hg remains fixed at 0.007%
Contains Thiomersal
Expanded Jurisdictional Detail
Additional regulatory detail beyond the 7-jurisdiction summary: Saudi SFDA, Korea MFDS, ASEAN ACD, Japan/Korea, Brazil/India, and cross-jurisdictional restriction entries.
SA Saudi SFDA (V - Preservatives)
Product type: Eye products. Max: 0.007% (of Hg) If mixed with other mercurial compounds authorized by this Regulation, the maximum concentration of Hg remains fixed at 0.007%. Contains Thiomersal
BRIN Brazil/India Cosmetics
India: Permitted Preservative · max 0.007% (of Hg) If mixed with other mercurial compounds authorized by this Regulation, the maximum concentration of Hg remains fixed at 0.007%
Additional Jurisdictional Restrictions (6)
| Jurisdiction | Status | Max % | Product Type |
|---|---|---|---|
| IN | restricted | 0.007 | eye makeup and eye makeup remover ONLY |
| IN | permitted_preservative | 0.007 | eye makeup and eye makeup remover only |
| AU | banned | - | all |
| BR | banned | - | - |
| CA | banned | - | - |
| ASEAN | permitted_preservative | 0.007% as Hg (max total Hg 0.007% if mixed) | Eye make-up and eye make-up remover ONLY |
Expanded Dermal Absorption Data
Cross-database dermal penetration: EPA Dryad physics-based, Roberts Mendeley permeation, and SCCS-aggregated measured values.
Aggregated DA Values (2 records across 5 sources)
| Type | DA % | Method | Skin Model | SCCS Ref |
|---|---|---|---|---|
| default | 50.0 | method=default | - | - |
| default | 0.007 | method=default | - | - |
Additional Ingredient Properties
1 property record from structured ingredient metadata.
allergen_detail
{"eu_allergen_listed": "no", "allergen_class": "preservative", "cross_reactivity_group": "mercury-group", "patch_test_frequency_pct": "5.0", "sensitization_rate": "high", "common_reaction_type": "contact-dermatitis", "ifra_restricted": "no", "source": "ESSCA; IVDK; NACDG"}
PubChem Annotations
Safety and regulatory annotations from PubChem (NCBI) aggregated sources.
Safety (1)
Carcinogen Classification
No indication of carcinogenicity (not listed by IARC). (L135)
Source: Toxin and Toxin Target Database (T3DB)
Function Categories & List Membership
Cosmetic/Chemical Function Categories
Preservative
Regulatory List Membership (2)
EU Regulated in Personal Care
EU CosIng Cosmetics Ingredient Database
Expert Verdict
Expert safety assessment and concern-level summary for Thimerosal (Thiomersal).
Regulatory Flags
preservative
eu_cosing_listed
Dermal Absorption
View details ->| Absorption % | Method | Vehicle |
|---|---|---|
| 50.0 | method=default | - |
| 0.007 | method=default | - |
Known Synonyms
((o-Carboxyphenyl)thio)ethylmercury sodium salt
Merthiolate
Mercurate(1-), ethyl[2-(mercapto-.kappa.S)benzoato(2-)-.kappa.O]-, sodium (1:1)
Caswell No. 766
EINECS 200-210-4
EPA Pesticide Chemical Code 078901
Estivin
Ethyl (sodium o-mercaptobenzoato)mercury
Ethylmercurithiosalicyclic acid, sodium salt
Ethylmercurithiosalicylic acid sodium salt
Mercurate(1-), ethyl(2-mercaptobenzoate(2-)-O,S)-, sodium salt
Mercurate(1-), ethyl(o-mercaptobenzoato(2-))-, sodium
Mercurothiolatum
Mercury, ethyl(2-mercaptobenzoate-S)-, sodium salt
Mercury, ethyl(2-mercaptobenzoato-S)-, sodium salt
Merphol
Merthiolate salt
Merzonin sodium
Sodium ethylmercuric thiosalicylate
Thimerosalate
Chemical Function
Preservative
Regulatory Lists
Canada; pharmaceutical
pharmaceutical
active_ingredient; animal_products; Europe; pharmaceutical; residue
Europe; Personal care
Cross-Vertical Safety Context
Same-CAS public records found in pharmaceutical data.
SOURCE
ChEMBL / DrugCentral / FAERS
DB_PHARMA CAS match
Pharmaceutical Data
Same-CAS rows from the pharmaceutical spoke database.
Compound
thiomersal
ChEMBL ID
CHEMBL508338
Adverse Event Associations
20
Frequently Asked Questions
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.
Is Thimerosal (Thiomersal) used outside cosmetics?
Thimerosal (Thiomersal) also appears in industrial chemical safety and pharmaceutical data. The cross-vertical cards on this page render same-CAS public rows from the matched databases.
Does Thimerosal (Thiomersal) have different safety status in cosmetics vs industrial chemicals?
Thimerosal (Thiomersal) is prohibited in EU cosmetics but has active industrial GHS classifications (H301, H317, H320, H341, H351, H360, H371, H372).
Compliance Tools
Check Thimerosal (Thiomersal) compliance across multiple jurisdictions:
Ingredient Decoder
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82 Allergen Checker
Check for EU declarable fragrance allergens
Substance Compliance
Check compliance across multiple jurisdictions
MoS Calculator
Calculate Margin of Safety using SCCS methodology
Heavy Metal Limits
Compare limits across jurisdictions
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THIMEROSAL
Moderate
Chemical family
Preservative
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