Why does CAS 533-73-3 appear in more than one EU cosmetic annex?

A substance identified by CAS 533-73-3 may appear in multiple EU cosmetic regulation annexes when it is subject to different conditions in different contexts — for example, restricted under Annex III with specific conditions, while also appearing in Annex IV as an approved colorant under separate entry conditions. Each entry must be reviewed individually.

How do I check if my formula contains a substance with CAS 533-73-3?

Use the INCI Checker on CosIng Checker with INCI names, CAS numbers or EC numbers. Paste CAS 533-73-3 to screen it directly, then review every linked annex record and supplier document.

CAS 1 record

CAS 533-73-3

Q: How do I use CAS 533-73-3 for compliance screening?

Cross-reference CAS 533-73-3 against your raw material specification sheets and CoA documents. When it appears in Annex II, verify absence. When it appears in Annex III, verify that concentration limits and product type conditions are met. All annex entries sharing this CAS number are listed on this page.

CAS 533-73-3 matches 1 EU annex record across Annex II–VI of Regulation 1223/2009.

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Chemical identity and properties

PubChem 2D chemical structure for CAS 533-73-3

CAS 533-73-3PubChem CID 10787

1,2,4-Benzenetriol

Benzene-1,2,4-triol is a benzenetriol carrying hydroxy groups at positions 1, 2 and 4. It has a role as a mouse metabolite. — ChEBI

IUPAC name: benzene-1,2,4-triol

Molecular formula: C6H6O3
Molecular weight: 126.11 g/mol
Exact mass: 126.031694049 Da
XLogP3: 1.5
Topological polar surface area: 60.7 Å²
Hydrogen-bond donors: 3
Hydrogen-bond acceptors: 3
Covalent units: 1
Defined stereocentres: 0

Also known as

1,2,4-TrihydroxybenzeneHydroxyhydroquinoneHydroxyquinol4-HydroxycatecholIMEXINE OAM173O8B04RDNSC-2818CHEBI:16971

16 more reported names

RefChem:71511208-575-1Oxyhydroquinone2,5-DihydroxyphenolOxyhydrochinonHydroquinone, hydroxy-1,3,4-Trihydroxybenzene1,3,4-BenzenetriolNSC 2818Oxyhydrochinon [German]CCRIS 2987EINECS 208-575-1BRN 2042863UNII-173O8B04RDAI3-193611,4-Benzenetriol

Open full PubChem record PubChem annotations 3D structure image

External database identifiers

ChEBI:CHEBI:16971
ChEMBL:CHEMBL3092389
EPA DTXSID:DTXSID3040930
PubMed:39245080
PubMed:30327826
PubMed:24530881
PubMed:23776099
PubMed:23022512
PubMed:22701692
PubMed:22380602
PubMed:22292983
PubMed:22200301
PubMed:22102096
PubMed:22073085
PubMed:21912624

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

Records for CAS 533-73-3

1 total

Annex

Entry

1642

1,2,4-Trihydroxybenzene when used as a substance in hair and eyelash dye products

208-575-1

How CAS 533-73-3 is used on this site

CAS 533-73-3 is the Chemical Abstracts Service identifier used to pin this page to a specific substance. In the current dataset, 1 EU annex record shares this identifier, which helps you cross-check whether the same substance appears under one regulatory context or several.

Use this page when a supplier specification, SDS or raw-material dossier gives you CAS 533-73-3 and you need to see every linked Annex II–VI record in one place. The entry cards above are the quickest route to concentration limits, warnings, annex placement and product-type conditions.

Frequently asked questions

A substance identified by CAS 533-73-3 may appear in multiple EU cosmetic regulation annexes when it is subject to different conditions in different contexts. For example, a substance might be restricted under Annex III with specific conditions, and the same CAS might also appear in Annex IV as an approved colorant under separate entry conditions. Each entry must be reviewed individually.

Cross-reference the CAS number against your raw material specification sheets and CoA documents. When a CAS appears in Annex II, verify absence. When it appears in Annex III, verify that concentration limits and product type conditions are met in your formulation. All annex entries sharing this CAS number are listed above.

A CAS number is assigned by the Chemical Abstracts Service (USA) and is globally recognised. An EC number is a European Commission identifier from inventories such as EINECS, ELINCS or the NLP list. Both identifiers may appear in EU cosmetic annex entries. Some substances have both, some have only one, and some older entries may have neither.

The INCI Checker accepts ingredient names, CAS numbers and EC numbers. Check this CAS number directly, then verify the result against supplier specification sheets and every linked annex condition.

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