Ingredient Dictionary

CYSTEINE HCL

L-cysteine hydrochloride is a hydrochloride obtained by combining L-cysteine with one molar equivalent of hydrogen chloride.

How much products actually contain

No product states its amount yet.

Of the products containing it, 1 list it before the 1% line and 3 after it (usually 1% or less).

Products using this ingredient

4 of 4 confirmed · likeliest to carry enough first

Definition

L-cysteine hydrochloride is a hydrochloride obtained by combining L-cysteine with one molar equivalent of hydrogen chloride. It has a role as a flour treatment agent, an EC 4.3.1.3 (histidine ammonia-lyase) inhibitor and a human metabolite. It contains a L-cysteinium.

Source: PubChem

US FDA substance register · UNII A9U1687S1S · registered name CYSTEINE HYDROCHLORIDE ANHYDROUS · single chemical substance

Source: US FDA Unique Ingredient Identifier (UNII)

Cosmetic roles

Softens hairHAIR CONDITIONINGCurls or straightens hairHAIR WAVING OR STRAIGHTENINGReduces other ingredientsREDUCINGSlows spoilage by oxygenANTIOXIDANT

Safety & regulatory references

Restricted: South Korea · Taiwan

Source: MFDS (Korea) cosmetic regulatory information

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 システインＨＣｌ: 本品は、システイン（＊）の塩酸塩であり、次の化学式で表される。

Source: JCIA labelling names (Japan)

Names & identifiers

CYSTEINE HCLINCI시스테인에이치씨엘Korean label name (MFDS standard)L-Cysteine, hydrochloride (1:1)SynonymシステインＨＣｌJapanese labelling name

CAS No.chemical registry number: 52-89-1
CAS No.chemical registry number: 7048-04-6
EC No.EU chemical inventory number: 200-157-7
DTXSIDUS EPA chemical ID: DTXSID0020367
DTXCIDUS EPA compound ID: DTXCID60367

IUPAC: L-Cysteine--hydrogen chloride (1/1)
Molecular formula: C3H8ClNO2S
Molecular weight: 157.61 g/mol

Measured properties

Appearance: Dry Powder · Solid, [Sigma-Aldrich MSDS]
Colour: white
Melting/freezing point: 175 ℃
n-Octanol/water partition coefficient (Kow): -3.05
Decomposition temperature: 175-178 ℃
Molecular weight: 157.62

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 15 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
Antioxidant2
Softener and conditioner2
Hair waving or straightening (EPA)2
Reducing agent2
Food preservative (EPA)1
Filler1
Leavening agent (EPA)1

Source: US EPA CompTox dashboard

Irritation and sensitisation studies

3 skin studies and 1 eye studies are on record.

Classed as low3

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 4 studies

Not likely to be sensitizing
skin sensitisation: in vivo (LLNA) · Screening · according to OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Not likely to be sensitizing
skin sensitisation: in vivo (LLNA) · Screening · according to OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay) 2010, July 22 according to EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Studies Indicate No Significant Irritation
skin irritation: in vivo · Screening · other guideline: OECD 402 according to
Studies Indicate No Significant Irritation
eye irritation: in vivo · Screening · OECD Guideline 405 (Acute Eye Irritation / Corrosion) according to