How much products actually contain
11 products state the amountmedian 0.000029%
- under 0.01% 7
- 0.01–0.1% 1
- 0.1–1% 1
- 1% or more 2
Amounts are mostly stated by products named after the ingredient, so they may lean towards token amounts.
Of the products containing it, 95 list it before the 1% line and 380 after it (usually 1% or less).
Products using this ingredient
12 of 475 confirmed · likeliest to carry enough first · See all 475
KIOSKINKIOSKIN L-Cysteine Melacare Intensive Cream1% stated
KIOSKINKIOSKIN L-Cysteine Melacare Light-Up Sun Cream1% stated
KIOSKINKIOSKIN L-Cysteine Melacare Sun Cream0.5% stated
ElastineAmino Peptide Weak Acid Protein High Nutrition Shampoo Pear & Freesia Scent0.000029% stated
PurcellPurcell 88 Billion/mL Glutathione Flexible Liposome Tone-Up Ampoule 20ml
LEADERSInsolution Aquaringer Skin Clinic Mask
RootecaRooteca Root Enhancing Ampoule Shampoo 200ml (Single)
Wander BeautyWander Beauty Baggage Claim™ Eye Masks
Paul MitchellPaul Mitchell Lavender Mint Moisturizing Shampoo
UNOVEUNOVE Volume Up Hair Fixer 200ml
MEDIPEELMelanon X Cream
MEDIPEELMEDIPEEL Melanon X Cream
Cosmetic roles
Softens hairHAIR CONDITIONINGCurls or straightens hairHAIR WAVING OR STRAIGHTENINGReduces other ingredientsREDUCINGListed as a fragrance-composition material (not a claim that it adds scent)FRAGRANCESlows spoilage by oxygenANTIOXIDANTReduces staticANTISTATIC
Safety & regulatory references
- Restricted
- South Korea · Taiwan
Source: MFDS (Korea) cosmetic regulatory information
Other restriction: ban substances that deplete the ozone layer
Source: EU CosIng ingredient list
Reviewed by CIR: Safety Assessment of alpha-Amino Acids as Used in Cosmetics
More data — names, identifiers, properties, test records, literature
Official labels & definitions
JCIA labelling name システイン: 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
CYSTEINEINCI시스테인Korean label name (MFDS standard)システインJapanese labelling name
- CAS No.chemical registry number
- 3374-22-9
- CAS No.chemical registry number
- 52-90-4
- EC No.EU chemical inventory number
- 200-158-2
- EC No.EU chemical inventory number
- 222-160-2
Measured properties
- Appearance
- Colorless or white solid, [HSDB] Colorless crystalline solid, [Sigma-Aldrich MSDS] · Solid
- Melting point
- 240 dec °C · 260 °C decomposes
- Solubility
- 277000 mg/L (at 25 °C) · Freely soluble in water
- Stability
- Stable under recommended storage conditions. · In neutral or slightly alkaline aq solns it is oxidized to cystine by air. More stable in acidic solns.
- Dissociation constant
- 1.71 · pK1 1.71 /carboxylic/, pK2 8.33 /amine/, pK3 10.78 /sulfide/
Values measured on the substance itself, not a specification for a commercial raw material.
Source: PubChem
Related literature
- Safety and efficacy of the feed additives l‐cysteine and l‐cysteine hydrochloride (monohydrate and anhydrous) for all animal species (Wacker Chemie AG) · 2025
- Mutations in the ilvN gene mitigate growth inhibitory effect of cysteine in Corynebacterium glutamicum · 2025
- Challenges and Advances in the Bioproduction of L-Cysteine · 2024
- Synthesis, Antioxidative and Whitening Effects of Novel Cysteine Derivatives · 2017
- Convergent evolution of cysteine-rich proteins in feathers and hair · 2015
Linked databases 17
- Australian Industrial Chemicals Inventory (AICIS)
- ChEBI 2
- ChEMBL 2
- China inventory of existing ingredients (IECIC)
- EU CosIng ingredient list 2
- JCIA labelling names (Japan)
- Korea Cosmetic Association ingredient dictionary
- MFDS (Korea) cosmetic ingredient register 2
- MFDS (Korea) cosmetic regulatory information 2 3
- NIST Chemistry WebBook 2
- PubChem
- Tlooto literature search 2 3 4 5
- UniChem cross-reference IDs 2
- US Cosmetic Ingredient Review (CIR) 2
- US EPA DSSTox chemical database 2
- US FDA substance registration (GSRS) 2
- Wikidata 2 3