Thiamidol

Best-in-class human tyrosinase inhibitor approximately 15x more potent than hydroquinone with critical mechanistic safety advantage as a strictly competitive reversible inhibitor that cannot form cytotoxic quinones. 2025 RCT (n=90) demonstrated visible improvement by objective colorimetry from week 2 through 12 weeks with regression-phase durability across melasma, solar lentigines, and acne-induced PIH in all phototypes including Fitzpatrick IV–VI with no adverse effects. Post-market evidence covers >50 million products and >120 studies since 2018 launch. The EU classifies Thiamidol as "permitted". Safety rating: EXCELLENT.

Thiamidol EU regulatory status: permitted. This is based on EU Regulation 1223/2009 and its amendments.

Thiamidol functions as: Highly selective competitive reversible inhibitor of human tyrosinase (hTyr); most potent hTyr inhibitor identified from screen of >50,000 compounds; IC50 1.1 µM against hTyr vs hydroquinone IC50 16.3 µM (~15x more potent); does not act as a tyrosinase substrate — cannot generate cytotoxic quinones. It is classified as a Active Ingredient in our database. CAS number: 1802390-41-5.

adequate The Margin of Safety (MoS) is calculated using SCCS methodology. A MoS above 100 is generally considered safe. Use the MoS Calculator tool to calculate MoS for your specific formulation and product category.