Common Name(s): Thimerosal,thimerosal,prohibited mercury preservative,eu annex ii banned organomercury
CAS Number: N/a
DESCRIPTION
What It Does: Prohibited in eu cosmetics. thimerosal releases ethylmercury which binds thiol groups in neuronal proteins causing irreversible neurotoxicity — the risk/benefit assessment leaves no acceptable cosmetic use.
Why It's Used: Mercury bioaccumulation: ethylmercury from thimerosal crosses the blood-brain barrier, accumulates in cns, and causes irreversible neurological damage with no safe lower threshold established for cosmetic exposure routes.
How It Works: Ethylmercury-thiosalicylate → ethylmercury (hg²⁺) + thiosalicylate on tissue contact. hg²⁺ irreversibly binds cysteine thiol groups in neuronal enzymes, tubulin, and dna-repair proteins — preventing cell division and causing axonal degeneration.
Typically Found In: Prohibited
TECHNICAL DETAILS
Primary Category: Active ingredient – cosmetic active
Secondary Functions: Skin conditioning
Application Areas:
Facial Skincare
Body Care
Hair Care
Beard Care
Color Cosmetics (Makeup)
Dietary/Oral Supplements
Typical Concentration Range: Prohibited
SOURCING & ETHICS
Vegan Status: Conditional - supplier confirmation required
Halal Status: Unverified - supplier confirmation required
Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier. [audit 2026-07-29 rev2: the record's own source_notes does not assert a non-animal origin, or instructs the reader to verify with the supplier; "yes" asserts knowledge the record does not hold. determination requires shariah-panel sign-off.]
SKIN COMPATIBILITY
Irritancy Rating: 1/5 – very low
Comedogenicity Rating: 0/5 – non-comedogenic
Sensitivity Concerns: Well-tolerated by most skin types.
Safe for Sensitive Skin: Yes
SAFETY & COMPATIBILITY
Safety Profile: Good safety profile at recommended concentrations. ewg score: 1–2.
Works Well With: Standard skincare actives
Avoid Combining With: No known significant incompatibilities
SCIENTIFIC NOTE
Replace with: phenoxyethanol/ethylhexylglycerin, methylisothiazolinone-free systems, or broad-spectrum cosmos-accepted preservatives depending on formulation type.
Last Verified: 2026-03-22
Primary Sources: Eu regulation 1223/2009 annex ii,thimerosal mercury neurotoxin review