CYSTEINE
L-Cysteine
CYSTEINE is listed in the EU CosIng inventory, but no direct annex records are linked on this page yet.
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.
Chemical identity and properties
DL-cysteine
Cysteine is a sulfur-containing amino acid that is propanoic acid with an amino group at position 2 and a sulfanyl group at position 3. It has a role as a fundamental metabolite. It is a polar amino acid, a sulfur-containing amino acid and an alpha-amino acid. It contains a sulfanylmethyl group. It is a conjugate base of a cysteinium. It is a conjugate acid of a cysteinate(1-). It is a tautomer of a cysteine zwitterion. — ChEBI
- IUPAC name
- 2-amino-3-sulfanylpropanoic acid
- Molecular formula
- C3H7NO2S
- Molecular weight
- 121.16 g/mol
- Exact mass
- 121.01974964 Da
- XLogP3
- -2.5
- Topological polar surface area
- 64.3 Ų
- Hydrogen-bond donors
- 3
- Hydrogen-bond acceptors
- 4
- Covalent units
- 1
- Defined stereocentres
- 0
Also known as
16 more reported names
External database identifiers
- ChEBI:CHEBI:15356
- ChEMBL:CHEMBL54943
- EPA DTXSID:DTXSID5046988
- PubMed:23024785
- PubMed:22867025
- PubMed:22813754
- PubMed:22769850
- PubMed:22572786
- PubMed:22539321
- PubMed:22533155
- PubMed:22524145
- PubMed:22523489
- PubMed:22427952
- PubMed:22405311
- PubMed:22365687
Retrieved from NIH PubChem on 2026-08-31 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.
L-(+)-Cysteine
L-cysteine is an optically active form of cysteine having L-configuration. It has a role as a flour treatment agent, an EC 4.3.1.3 (histidine ammonia-lyase) inhibitor and a human metabolite. It is a cysteine, a L-alpha-amino acid, a serine family amino acid and a proteinogenic amino acid. It is a conjugate base of a L-cysteinium. It is a conjugate acid of a L-cysteinate(1-). It is an enantiomer of a D-cysteine. It is a tautomer of a L-cysteine zwitterion. — ChEBI
- IUPAC name
- (2R)-2-amino-3-sulfanylpropanoic acid
- Molecular formula
- C3H7NO2S
- Molecular weight
- 121.16 g/mol
- Exact mass
- 121.01974964 Da
- XLogP3
- -2.5
- Topological polar surface area
- 64.3 Ų
- Hydrogen-bond donors
- 3
- Hydrogen-bond acceptors
- 4
- Covalent units
- 1
- Defined stereocentres
- 1
Also known as
16 more reported names
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.
Inventory details for CYSTEINE
INCI name
CYSTEINE
INN name
cysteine
Description
L-Cysteine
Record provenance
- Inventory reference
- 75422
- Imported identity
- CYSTEINE
- Source update
- 15/10/2010
Annex records for CYSTEINE
Key data
- ANTIOXIDANT
- Inhibiting reactions promoted by oxygen, thus avoiding oxidation and rancidity.
- ANTISTATIC
- Preventing and/or reducing static electricity by neutralising electrical charge on surfaces.
- FRAGRANCE
- Imparting an odour or taste. Creating a perceivable pleasant smell and/or masking a bad smell.
- HAIR CONDITIONING
- Enhancing the appearance and feel of hair. Leaving the hair easy to comb, supple, soft and shiny and/or imparting volume, lightness, gloss, texture, etc.
- HAIR WAVING OR STRAIGHTENING
- Modifying the chemical structure of the hair, allowing it to be set in the style required (permanent waves or hair straightening).
- REDUCING
- Changing the chemical nature of another ingredient by adding hydrogen (or removing oxygen).
Official EU ingredient-name evidence
The ingredient name exactly matches the official 2025 EU glossary of common ingredient names.
Related inventory evidence
Ingredients with overlapping formulation functions
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
How CYSTEINE appears in the CosIng inventory
The CosIng inventory lists CYSTEINE 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.
CYSTEINE is also tagged with 6 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
Source note for CYSTEINE
This page reproduces the CosIng inventory entry for CYSTEINE 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 CYSTEINE 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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