Skin Conditioning
CYSTEAMINE HCL
Safety score · 0–100
Fine
Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.
About
Cysteamine HCl — a thiol amine used in some pigmentation treatments. Strong odor, prone to oxidation, and can irritate; not a casual over-the-counter pick.
Cysteamine HCl (CAS 156-57-0) is a small thiol amine (beta-mercaptoethylamine hydrochloride) with orphan-drug status (Cystaran, Procysbi) for cystinosis. In cosmetic skincare it has emerged as a melanogenesis-modulating active for hyperpigmentation, competing with hydroquinone and tranexamic acid. The molecule is highly reactive, prone to oxidation, and malodorous, which limits formulation stability. Published patch-test data show moderate irritation potential. No formal CIR monograph on cosmetic cysteamine exists; use patterns rely on investigator-initiated trials at 5% in occluded short-contact application.
Function
Skin benefits
- Potent tyrosinase-inhibiting melanogenesis modulator
- Emerging alternative to hydroquinone in pigmentation
- Orphan-drug status for cystinosis (systemic data)
Known concerns
- Characteristic sulfurous odor — volatile thiol
- Irritant on broken or sensitive skin
- Oxidizes readily — formulation stability is difficult
- Emerging rather than fully CIR-reviewed cosmetic use
References
EU CosIng database
European Commission cosmetic ingredient registry — regulatory status, restrictions, authorised functions.
Related skin conditionings
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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.