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Annex II Entry 1343 13/08/2020

4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products

4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products 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: 1343

Chemical identity and properties

PubChem 2D chemical structure for CAS 2051-85-6
CAS 2051-85-6PubChem CID 16325

4-(Phenylazo)resorcinol

IUPAC name
4-phenyldiazenylbenzene-1,3-diol
Molecular formula
C12H10N2O2
Molecular weight
214.22 g/mol
Exact mass
214.074227566 Da
XLogP3
3.0
Topological polar surface area
65.2 Ų
Hydrogen-bond donors
2
Hydrogen-bond acceptors
4
Covalent units
1
Defined stereocentres
0

Also known as

2,4-Dihydroxyazobenzene1,3-Benzenediol, 4-(phenylazo)-1,3-Benzenediol, 4-(2-phenyldiazenyl)-RefChem:516611Sudan Orange GSolvent orange 1Ceres Orange GCeres Orange GN
16 more reported names
Sudan GFat Orange ABenzeneazoresorcinolC.I. Solvent Orange 1Sudan Yellow ARResinol Orange GFat Orange GSFat Orange RGCerisol Yellow GRGrasol Yellow RSFOrganol Orange 2JTertrogras Orange SGFat Victoria Yellow D1504 YellowC.I. Food Orange 3p-Phenylazoresorcinol
Open full PubChem recordPubChem annotations3D structure image
External database identifiers

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

4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products

Chemical / IUPAC name

4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920)

Regulatory information

Regulation

(EC) 2013/344

See every entry this act set

Identified ingredients

Key data

CAS
2051-85-6
EC
218-131-9
Annex
II
Entry number
1343

Inventory links for 4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products

Inventory Restriction reference
Ref 32700

CI 11920

CAS: 2051-85-6
EC: 218-131-9

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

Annex IV 7
Shared CAS number

CI 11920

CAS: 2051-85-6
EC: 218-131-9

What Annex II means for 4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products

4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products 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. 4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products 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 2051-85-6 is the unique numerical identifier assigned to 4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products 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 4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products

This page summarizes one Annex II record for 4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products 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 4-(Phenylazo)resorcinol (Solvent Orange 1; CI 11920) and its salts, when used as a substance in hair dye products, but confirm any final regulatory decision against the current official annex wording and source files.

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