Is HYDROXYECTOIN safe to use in EU cosmetics?

HYDROXYECTOIN is listed in the EU CosIng ingredient inventory with no direct annex restriction records linked at this time. Always verify against the current official CosIng database before formulating.

What function does HYDROXYECTOIN serve in cosmetics?

According to the EU CosIng inventory, HYDROXYECTOIN carries the following function designation(s): BUFFERING, SKIN CONDITIONING, SKIN CONDITIONING - EMOLLIENT.

What other records share CAS 165542-15-4?

CAS 165542-15-4 may appear across multiple EU annex records. The CAS lookup page shows all Annex II–VI entries sharing this identifier, useful for identifying cross-annex regulatory status of the same chemical substance.

How do I check if my formula contains HYDROXYECTOIN?

Use the INCI Checker to screen a full ingredient list across selected markets, or use the substance market comparison to review this identity across all supported market datasets.

InventoryRef 8554115/10/2010

HYDROXYECTOIN

(4S,5S)-5-hydroxy-2-methyl-3,4,5,6-tetrahydropyrimidine-4-carboxylic acid

HYDROXYECTOIN is listed in the EU CosIng inventory, but no direct annex records are linked on this page yet.

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Regulatory evidence by market

No rule for this ingredient has been imported for any of the 13 markets tracked here.

That describes this inventory, not the law. No imported rule is not evidence that an ingredient is permitted: a rule may exist under another name or identifier, or in a dataset not yet imported here.

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Chemical identity and properties

PubChem 2D chemical structure for CAS 165542-15-4

CAS 165542-15-4PubChem CID 12011795

5-Hydroxyectoine

5-hydroxyectoine is a carboxamidine heterocycle which is obtained by formal condensation of 4-amino-L-allothreonine with acetic acid. It is a monocarboxylic acid, a carboxamidine, a secondary alcohol and a member of 1,4,5,6-tetrahydropyrimidines. It is a conjugate acid of a 5-hydroxyectoinate. It is a tautomer of a 5-hydroxyectoine zwitterion. — ChEBI

IUPAC name: (5S,6S)-5-hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidine-6-carboxylic acid

Molecular formula: C6H10N2O3
Molecular weight: 158.16 g/mol
Exact mass: 158.06914219 Da
XLogP3: -1.2
Topological polar surface area: 81.9 Å²
Hydrogen-bond donors: 3
Hydrogen-bond acceptors: 4
Covalent units: 1
Defined stereocentres: 2

Also known as

(4S,5S)-5-Hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidine-4-carboxylic acidCHEBI:49432RefChem:789461(4S,5S)-5-hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidin-3-ium-4-carboxylate(5S,6S)-5-hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidin-1-ium-6-carboxylateHydroxyectoinHydroxyectoinebeta-hydroxyectoine

16 more reported names

Thp(A)4-pyrimidinecarboxylic acid, 1,4,5,6-tetrahydro-5-hydroxy-2-methyl-, (4S,5S)-Ronacare hydroxyectoinCIJ7YN252E(S,S)-.BETA.-HYDROXYECTOINE(4S,5S)-2-methyl-4-carboxy-5-hydroxy-3,4,5,6-tetrahydropyrimidine(S,S)-1,4,5,6-Tetrahydro-5-hydroxy-2-methyl-4-pyrimidinecarboxylic acid4-Pyrimidinecarboxylic acid, 1,4,5,6-tetrahydro-5-hydroxy-2-methyl-, (S-(R*,R*))-Hydroxyectoine, primary pharmaceutical reference standard(4S,5S)-5-hydroxy-2-methyl-3,4,5,6-tetrahydropyrimidine-4-carboxylic acid(S,S)-2-methyl-5-hydroxy-1,4,5,6-tetrahydropyrimidine-4-carboxylic acidUNII-CIJ7YN252E(S,S)-beta-HydroxyectoineHydroxy ectoinePyrosHydroxy ection

Open full PubChem record PubChem annotations 3D structure image

External database identifiers

ChEBI:CHEBI:49432
ChEMBL:CHEMBL1230488
EPA DTXSID:DTXSID80167963

Retrieved from NIH PubChem on 2026-08-31 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Inventory details for HYDROXYECTOIN

INCI name

HYDROXYECTOIN

Description

(4S,5S)-5-hydroxy-2-methyl-3,4,5,6-tetrahydropyrimidine-4-carboxylic acid

Record provenance

Inventory reference: 85541
Imported identity: HYDROXYECTOIN
Source update: 15/10/2010

European Commission CosIng source notes

Annex records for HYDROXYECTOIN

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Key data

CAS

165542-15-4

442-870-8

Restriction

—

Function

BUFFERING: Stabilising the pH of an aqueous medium in a narrow range even if an acid or base is added. Altering and/or maintaining a cosmetic product's pH at the desired level.
SKIN CONDITIONING: Maintaining the skin in good condition.
SKIN CONDITIONING - EMOLLIENT: Acting as lubricants on the skin surface providing the skin with a soft and smooth appearance.

Official EU ingredient-name evidence

The ingredient name exactly matches the official 2025 EU glossary of common ingredient names.

#13226 · HYDROXYECTOIN

Ingredients with overlapping formulation functions

GUANIDINE HCLBUFFERING

HUMAN DERMAL FIBROBLAST STEM CELL EXOSOMESBUFFERING; HAIR CONDITIONING; EYELASH CONDITIONING; SKIN CONDITIONING - MISCELLANEOUS

HYDROBROMIC ACIDBUFFERING

HYDROCHLORIC ACIDBUFFERING

HYDROXYETHYLPIPERAZINE ETHANE SULFONIC ACIDBUFFERING

IMIDAZOLEBUFFERING

ISOBUTYRIC ACIDBUFFERING

ISOPROPANOLAMINEBUFFERING

Additional official and scientific sources

11 external databases to check this identity in

Each link searches that source for this identity. What each source is, and its legal weight

ECHA CHEM / Information on chemicals PubChem PUG REST EU Safety Gate cosmetic product alerts ECHA CHEM US EPA CompTox Cosmetic Ingredient Review safety assessments FDA Global Substance Registration System ILO/WHO International Chemical Safety Cards Japan NITE-CHRIP NIOSH Pocket Guide to Chemical Hazards OECD eChemPortal

How HYDROXYECTOIN appears in the CosIng inventory

The CosIng inventory lists HYDROXYECTOIN as a cosmetic ingredient and this page links it to 0 annex records. The inventory entry captures names and identifiers, while the annex records show where the substance is prohibited, restricted or positively listed in EU cosmetics law.

HYDROXYECTOIN is also tagged with 3 cosmetic functions in the official data. Function labels describe intended use, but they do not replace regulatory review of linked annex records before formulation or labelling work.

Frequently asked questions

HYDROXYECTOIN is listed in the EU CosIng ingredient inventory with no direct annex restriction records linked at this time. Absence of an annex link does not guarantee unrestricted use — always verify against the current official CosIng database before formulating.

According to the EU CosIng inventory, HYDROXYECTOIN carries the following function designation(s):

CAS 165542-15-4 may appear across multiple EU annex records. Viewing the CAS lookup page shows all Annex II–VI entries sharing this identifier, which is useful for identifying cross-annex regulatory status of the same chemical substance.

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Source note for HYDROXYECTOIN

This page reproduces the CosIng inventory entry for HYDROXYECTOIN from public European Commission cosmetic ingredient materials and shows linked identifiers even when no direct annex match is currently attached.

Use this inventory page to research HYDROXYECTOIN and compare linked records, but verify restrictions and legal status against the current official source text and law before making regulatory decisions.

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