Skin Brightening
CYSTEAMINE SULFATE
Safety score · 0–100
Moderate
Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.
A thiol-based pigment-reducing active — effective but irritating and famously malodorous. Short-contact, rinse-off use only; expect careful formulation.
Cysteamine sulfate (CAS 156-57-0 as HCl / 16214-16-7 as sulfate) is a sulfur-containing aminothiol used as a non-hydroquinone depigmenting active. Peer-reviewed clinical trials show efficacy against melasma at 5% in short-contact applications. Drawbacks are substantial: strong sulfur odour from H2S release, documented irritation, contact dermatitis, and formulation instability requiring oxygen-barrier packaging. Legal status varies — in the EU it is not listed as a conventional permitted cosmetic ingredient, so products are marketed as dermocosmetic in specific channels; in the US it sits in a grey area between cosmetic and OTC.
Skin benefits
- Non-hydroquinone melanin-inhibiting activity
- Active ingredient in dermatology-grade brightening products
Known concerns
- Strong characteristic sulfur odour
- Documented contact dermatitis and irritation
- Requires short contact time and rinse-off use
- Not universally permitted as a cosmetic ingredient — often positioned as OTC/drug
- Formulation instability — releases H2S on degradation
References
EU CosIng database
European Commission cosmetic ingredient registry: regulatory status, restrictions, authorised functions.
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This profile is for educational purposes and does not constitute medical advice. Regulatory status and scientific understanding evolve, so always read the physical product label and consult a healthcare professional for personal concerns.