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Annex II Entry 418 20/10/2010

3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester

3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester is listed in Annex II as a prohibited substance for cosmetic products placed on the EU market.

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Prohibited substance— Annex II, EU Regulation 1223/2009
Entry: 418

Chemical identity and properties

PubChem 2D chemical structure for CAS 104-98-3
CAS 104-98-3PubChem CID 736715

Urocanic Acid

Urocanic acid is an alpha,beta-unsaturated monocarboxylic acid that is prop-2-enoic acid substituted by a 1H-imidazol-4-yl group at position 3. It is a metabolite of hidtidine. It has a role as a chromophore and a human metabolite. It is a member of imidazoles and an alpha,beta-unsaturated monocarboxylic acid. It is a conjugate acid of a urocanate. — ChEBI

IUPAC name
(E)-3-(1H-imidazol-5-yl)prop-2-enoic acid
Molecular formula
C6H6N2O2
Molecular weight
138.12 g/mol
Exact mass
138.042927438 Da
XLogP3
0.0
Topological polar surface area
66.0 Ų
Hydrogen-bond donors
2
Hydrogen-bond acceptors
3
Covalent units
1
Defined stereocentres
0

Also known as

Urocaninic acid(2E)-3-(1H-imidazol-4-yl)prop-2-enoic acid3-(1H-Imidazol-4-yl)-2-propenoic acid2-Propenoic acid, 3-(1H-imidazol-4-yl)-G8D26XJJ3BNSC-663572-Propenoic acid, 3-(1H-imidazol-4-yl)-, (E)-CHEBI:27248
16 more reported names
Acid, UrocanicGlyoxalinylacrylic AcidAcid, GlyoxalinylacrylicRefChem:901492203-258-43-(1H-imidazol-5-yl)prop-2-enoic acidtrans-Urocanic acid4-imidazoleacrylic acid3465-72-3urocanateimidazoleacrylic acid(E)-3-(1H-imidazol-5-yl)acrylic acid5-Imidazoleacrylic acid(2E)-3-(1H-IMIDAZOL-4-YL)ACRYLIC ACID(E)-3-(4-Imidazolyl)acrylic acid3-Imidazol-4-ylacrylic acid
Open full PubChem recordPubChem annotations3D structure image
External database identifiers

Evidence from additional scientific databases

NIH PubChem PUG-View
Exact identifier match736715

Attributed physical-property, hazard, environmental and use annotations.

  • Cosmetic Ingredient Review Conclusion: The safety of this ingredient has not been documented and substantiated. The CIR Expert Panel cannot conclude whether Urocanic Acid is safe for use in cosmetic products until such time as the appropriate safety data have been obtained and evaluated. Source: Cosmetic Ingredient Review (CIR)
  • Cosmetic Ingredient Review Finding(s): Ingredients for which the data are insufficient and their use in cosmetics is not supported Source: Cosmetic Ingredient Review (CIR)

Mapped by: Existing checksum-valid CAS to unique PubChem CID match. Retrieved: 2026-08-31. Open source record

Scientific classifications and hazard annotations provide context and do not replace the market-specific regulatory decision shown above.

Additional source coverage and match status
SourceResultChecked
EMBL-EBI ChEBINeeds review2026-08-31
NIH PubChem PUG-ViewExact match2026-08-31

A recorded no-match is useful evidence that the source was checked; it is not a claim that the substance does not exist elsewhere.

Retrieved from NIH PubChem on 2026-09-02 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

PubChem 2D chemical structure for CAS 27538-35-8
CAS 27538-35-8PubChem CID 6365633

Ethyl urocanate

IUPAC name
ethyl (E)-3-(1H-imidazol-5-yl)prop-2-enoate
Molecular formula
C8H10N2O2
Molecular weight
166.18 g/mol
Exact mass
166.074227566 Da
XLogP3
0.7
Topological polar surface area
55.0 Ų
Hydrogen-bond donors
1
Hydrogen-bond acceptors
3
Covalent units
1
Defined stereocentres
0

Also known as

Parasonarl Mark II(E)-Urocanic acid ethyl esterUNII-GS4W88OP01GS4W88OP01EINECS 248-515-1Ethyl (E)-3-(1H-imidazol-4-yl)-2-propenoate2-Propenoic acid, 3-(1H-imidazol-4-yl)-, ethyl ester, (2E)-2-Propenoic acid, 3-(1H-imidazol-4-yl)-, ethyl ester, (E)-
16 more reported names
2-Propenoic acid, 3-(1H-imidazol-5-yl)-, ethyl ester, (2E)-3-(1H-Imidazol-4-yl)-2-propenoic acid, ethyl ester2-Propenoic acid, 3-(1H-imidazol-4-yl)-, ethyl esterRefChem:139070ETHYL UROCANATE [INCI](e)-3-(1h-imidazol-4-yl)-2-propenoic acid ethyl esterEthyl (2E)-3-(1H-imidazol-4-yl)prop-2-enoateethyl (2E)-3-(1H-imidazol-5-yl)prop-2-enoateEthyl 3-(1H-imidazol-4-yl)acrylateHPMLGOFBKNGJAM-ONEGZZNKSA-NEthyl (E)-3-(4-Imidazolyl)acrylateAS-48227(E)-ethyl 3-(1H-imidazol-4-yl)acrylateethyl (E)-3-(1H-imidazol-5-yl)acrylateEN300-1455951Ethyl(2E)-3-(1H-imidazol-4-yl)prop-2-enoate
Open full PubChem recordPubChem annotations3D structure image

Retrieved from NIH PubChem on 2026-09-02 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Record details

Chemical name

3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester

Regulatory information

Regulation

(EC) 2009/1223

See every entry this act set

Identified ingredients

Key data

CAS
27538-35-8 / 104-98-3
EC
248-515-1 / 203-258-4
Annex
II
Entry number
418

Inventory links for 3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester

Inventory Restriction reference
Ref 84570

ETHYL UROCANATE

CAS: 27538-35-8
EC: 248-515-1
Inventory Restriction reference
Ref 84613

UROCANIC ACID

CAS: 104-98-3
EC: 203-258-4

Direct matches are limited for this record, so nearby entries from Annex II are shown as well.

What Annex II means for 3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester

3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester is listed as a prohibited substance under Annex II of EU Cosmetics Regulation 1223/2009 and must not be intentionally added. Article 17 separately addresses unintended small quantities that are technically unavoidable under good manufacturing practice and compatible with the Article 3 safety requirement.

Formulators must screen their ingredients and raw materials to ensure none contain this substance. Suppliers should provide documentation confirming absence when requested.

This record is linked to 2 CosIng inventory ingredients for name and identifier cross-reference. The page also surfaces 12 related annex records with overlapping identifiers, annex logic or naming patterns.

Compliance checklist

  • Verify this substance is absent from all raw materials and finished formulations.
  • Request absence confirmation or CoA from raw material suppliers.
  • Document the screening result in the Product Information File (PIF).

Frequently asked questions

Yes. 3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester is listed in Annex II of EU Cosmetics Regulation 1223/2009 and is prohibited as an intentionally added cosmetic ingredient. Article 17 provides a narrow exception for unintended small quantities that are technically unavoidable under good manufacturing practice, provided the product remains safe under Article 3.

CAS 27538-35-8 / 104-98-3 is the unique numerical identifier assigned to 3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester by the Chemical Abstracts Service. In cosmetic compliance work, the CAS number is used to cross-reference the substance across regulatory databases, raw material specifications and safety assessment reports. Multiple EU annex entries may share the same CAS number if the same substance appears under different conditions or in different annexes.

Use the INCI Checker tool on this site to paste your full ingredient list (INCI) and scan it against all Annex II–VI entries. The tool highlights any ingredients that match restricted, prohibited or allergen-flagged records. This is useful for rapid compliance screening of finished product formulas or raw material declarations.
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Source note for Annex II record 3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester

This page summarizes one Annex II record for 3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester from public European Commission cosmetic materials and adds linked inventory or identifier matches when available.

Use this record page to review Annex II conditions for 3-Imidazol-4-ylacrylic acid (Urocanic acid) and its ethyl ester, but confirm any final regulatory decision against the current official annex wording and source files.

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