Are there usage precautions?

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All ingredients

Ingredient Dictionary

CYSTINE

L-cystine is the L-enantiomer of the sulfur-containing amino acid cystine.

How much products actually contain

No product states its amount yet.

Of the products containing it, 9 list it before the 1% line and 25 after it (usually 1% or less).

Products using this ingredient

12 of 33 confirmed · likeliest to carry enough first · See all 33

Definition

L-cystine is the L-enantiomer of the sulfur-containing amino acid cystine. It has a role as an EC 1.2.1.11 (aspartate-semialdehyde dehydrogenase) inhibitor, a flour treatment agent, a mouse metabolite, a Saccharomyces cerevisiae metabolite and a human metabolite. It is a cystine, a non-proteinogenic L-alpha-amino acid and a L-cysteine derivative. It is a conjugate acid of a L-cystine anion. It is an enantiomer of a D-cystine. It is a tautomer of a L-cystine zwitterion.

Source: PubChem

US FDA substance register · UNII 48TCX9A1VT · registered name CYSTINE · single chemical substance

Source: US FDA Unique Ingredient Identifier (UNII)

Cosmetic roles

Reduces staticANTISTATICSoftens hairHAIR CONDITIONINGListed as a fragrance-composition material (not a claim that it adds scent)FRAGRANCE

Safety & regulatory references

Not classified under Korea’s toxic-substance GHS list · existing chemical substance

Source: Korea toxic substances GHS register (NIER)

Reviewed by CIR: Safety Assessment of alpha-Amino Acids as Used in Cosmetics

Source: US Cosmetic Ingredient Review (CIR)

More data — names, identifiers, properties, test records, literature

Official labels & definitions

JCIA labelling name シスチン: 本品は、次の化学式で表されるアミノ酸である。

Source: JCIA labelling names (Japan)

Names & identifiers

CYSTINEINCI시스틴Korean label name (MFDS standard)L-CystineSynonymシスチンJapanese labelling name

CAS No.chemical registry number: 56-89-3
EC No.EU chemical inventory number: 200-296-3
DTXSIDUS EPA chemical ID: DTXSID2046418
DTXCIDUS EPA compound ID: DTXCID0026418

IUPAC: L-Cystine
Molecular formula: C6H12N2O4S2
Molecular weight: 240.29 g/mol

Measured properties

Appearance: Solid, [Merck Index] White powder, [Sigma-Aldrich MSDS] · Solid
Melting point: 260.5 dec °C · 260.5 °C
Solubility: 190 mg/L (at 20 °C) · 0.19 mg/mL
Dissociation constant: 1
Colour: white
Initial boiling point and range: (ECHA)
Flammability (solid, gas): combustible
Vapour pressure: 0.000000000212 ㎜Hg (@ 25 ℃, est.)
Water solubility: 190 ㎎/ℓ (20℃)
Vapour density: 8.29
Relative density: 1.66 (@ 20 ℃)
n-Octanol/water partition coefficient (Kow): -5.08
Auto-ignition temperature: 286 ℃
Decomposition temperature: 260.5 ℃
Molecular weight: 240.30048

Values measured on the substance itself. The KOSHA data are a reference for writing and reviewing safety data sheets, not a specification for a commercial raw material.

Source: PubChem · KOSHA safety data sheets (Korea)

What products actually use it for

What the 8 products reported to the US EPA with this ingredient use it for. Products outside cosmetics are included, so the top few rows are its main uses.

Flavouring and nutrient4
Filler1
Softener and conditioner1
Anti-static agent1
Deodorizer1

Source: US EPA CompTox dashboard

Irritation and sensitisation studies

1 skin studies and 0 eye studies are on record.

Classed as low1

The study conclusions largely agree (100%). These tests are on the raw material itself; irritation at the amount in a finished product is a different question.

See all 1 studies

Not likely to be sensitizing
skin sensitisation: in vivo (LLNA) · Screening · according to OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)