Is Thiamidol safe in cosmetics?
Thiamidol has a safety rating of "EXCELLENT" in our database. EU status: permitted. US status: permitted.
Excellent
Active Ingredient
Thiamidol
INCI: ISOBUTYLAMIDO THIAZOLYL RESORCINOL
Thiamidol (CAS 1802390-41-5) is a cosmetic active ingredient functioning as Highly selective competitive reversible inhibitor of human tyrosinase (hTyr);. EU Regulation 1223/2009 status: permitted. Industrial safety data is also available in the chemical safety database.
View industrial chemical safety profile for CAS 1802390-41-5 →
Auto-generated CPSR Part A draft with source citations
Function
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
Safety Rating
EXCELLENT
Regulatory Status
EU EU Status
permitted
US US Status
permitted
US Notes
No FDA restriction. Marketed in cosmetic brightening products globally. Not classified as a drug. Patent-protected by Beiersdorf; feature in Eucerin Anti-Pigment product line.
For full compliance data across multiple jurisdictions, use the Substance Compliance tool.
Safety Data
Margin of Safety, dermal absorption, and sensitization profile summaries for Thiamidol.
Calculate MoS for your specific formulation with the MoS Calculator.
Expert Verdict
Expert safety assessment and concern-level summary for Thiamidol.
Regulatory Flags
tyrosinase-inhibitor
brightening
best-in-class
most-potent-hTyr-inhibitor
50000-compound-screen
ic50-1.1uM
15x-more-potent-than-hq
strictly-competitive-reversible
no-quinone-formation
no-ochronosis
no-leukoderma
all-fitzpatrick-phototypes
fitzpatrick-iv-vi-safe
2025-rct-week-2-visible
melasma
solar-lentigo
pih
beiersdorf-proprietary
eu-allowed
us-allowed
Frequently Asked Questions
Is Thiamidol allowed in the EU?
Thiamidol EU regulatory status: permitted. This is based on EU Regulation 1223/2009 and its amendments.
What does Thiamidol do in cosmetics?
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.
Compliance Tools
Check Thiamidol compliance across multiple jurisdictions:
Ingredient Decoder
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82 Allergen Checker
Check for EU declarable fragrance allergens
Substance Compliance
Check compliance across multiple jurisdictions
MoS Calculator
Calculate Margin of Safety using SCCS methodology
Heavy Metal Limits
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THIMEROSAL
Moderate
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Preservative
THYMUS LINEARIS LEAF/(ANGELICA GLAUCA/BERGENIA CILIATA) ROOT/PRINSEPIA UTILIS SEED EXTRACT
Good
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Skin Conditioning
THYMUS SERPYLLUM EXTRACT
Good
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Skin Conditioning
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