Fragrance avoidance
No fragrance-linked caution surfaced in the current profile.
This ingredient does not currently read as a fragrance-linked driver in the published evidence and hazard profile.
4-HYDROXYINDOLE
4-Hydroxyindole, when used as a substance in hair dye products is prohibited in cosmetic products under Annex II of the EU Cosmetics Regulation (EC) 1223/2009.
Concern score
100/100Critical concern based on regulatory listings.
Well researched
How we scored this
The concern value reflects this ingredient's chemical identity — its hazard profile from the published classifications and regulatory status below — not the safety of a product it appears in. A score near 40 is the baseline for ingredients with no specific signal (water scores 40 by design), so a mid-range value is not a safety verdict.
Concern score 100/100 (critical) · high confidence.
Regional restrictions
- EU — banned · Annex II of EU Cosmetics Regulation (EC) 1223/2009: substances prohibited in cosmetic products.
Where it appears
Prevalence of 4-HYDROXYINDOLE in our catalog (epa_cpdat).
Brands
2
Typical roles
Dye
Suitability
Context-specific fit derived from published classifications and the current ingredient evidence profile.
Good fit
Evidence read
The published evidence profile currently shaping this ingredient record.
No evidence profiles are attached to this ingredient yet.
Linked research
Primary documents currently linked to this ingredient record.
No linked research documents are attached to this ingredient yet.
Extracted claims
Structured claim signals pulled from linked ingredient research.
No extracted claims are attached to this ingredient yet.
Regulatory status
Published jurisdiction-level classifications and regulatory designations for this ingredient.
EU
EC
Annex II of EU Cosmetics Regulation (EC) 1223/2009: substances prohibited in cosmetic products.
Effective: 2010-10-15View source →
US
EPA
EPA CPDat observed this chemical in 0 composition records across product categories including unclassified products. EPA CPDat classifies this chemical for functional uses including Dye.
Effective: 2020-02-13View source →
US
FDA