Antioxidant
THIOHISTIDINE
Safety score · 0–100
Caution
Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.
About
An amino acid derivative with significant hazard classifications including skin sensitization, serious eye irritation and respiratory irritation, this antioxidant ingredient requires careful handling and has limited cosmetic use.
Thiohistidine is a sulfur-containing amino acid derivative classified under the EU CLP regulation with hazard statements H302 (acute toxicity), H315 (skin irritation), H317 (skin sensitization), H319 (serious eye irritation), and H335 (respiratory irritation). While it appears in CosIng as having chelating and antioxidant functions, the compound's GHS classification as a skin sensitizer means it would likely require restriction under EU Annex III if used in cosmetic products above threshold concentrations. SCCS evaluation of similar amino acid derivatives suggests caution in leave-on formulations.
Function
Skin benefits
- Antioxidant properties
- Chelating agent for metal ions
- Bleaching agent
Known concerns
- Skin sensitizer (H317 - May cause allergic skin reaction)
- Serious eye irritant (H319)
- Acute toxicity hazard (H302)
- Skin irritant (H315)
- Respiratory irritant (H335)
- Limited cosmetic usage data
References
EU CosIng database
European Commission cosmetic ingredient registry — regulatory status, restrictions, authorised functions.
Related antioxidants
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This profile is for educational purposes and does not constitute medical advice. Regulatory status and scientific understanding evolve — always read the physical product label and consult a healthcare professional for personal concerns.