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Cystine
AKA “L-cystine, L-Dicysteine, beta, beta'-Dithiodialanine, L-Cysteine disulfide, 1-Cystine”
Hair Conditioning
Ingredient Facts
Cystine
AKA: L-cystine, L-Dicysteine, Beta, Beta'-Dithiodialanine, L-Cysteine disulfide, 1-Cystine
Hair Conditioning · Antistatic · EWG: 4
Synthetic
Skin Conditioner
Hair Care
Amino Acid
Medicated Active
Not Clean
Cystine
Effective at 3.0%
Formula
C6H12N2O4S2
Mol. Weight
240.3
CAS #
56-89-3
Form
Powder
See origin →
Functions
Antistatic
Hair Conditioning
A catch-all term for ingredients that improve how skin looks and feels — softer, smoother, more supple. The workhorse behind most moisturizers.
Anti-Inflammatory
Moisturizing
Brightening
Reduces flyaways
Softens and detangles hair
Provides scent
Traditional Use
The oxidized dimer form of cysteine, discovered in the early 19th century. Used in modern haircare since the 1970s-1980s to strengthen hair structure and improve resilience, mimicking natural protein bonds in keratin.
Skin Types
●all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Yes
EWG
4
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Not Phototoxic
medical-approval
all-shades-safe
Concentration Guide
0.0001%
6.0%
0%8%
Effective Range
CIR reported use: 0.0001-5 | 0.0001-6 | 0.001-3
Regulatory Status
USA✔ permitted
EU⚠ restricted
JAPAN⚠ restricted
CANADA⚠ restricted
Beta-Carotene.
, 2006
→
Inhibitory effect of prostaglandin E1 on laurate-induced peripheral vascular occlusive sequelae in rabbits: optimized topical formulation with beta-cy
Adachi H, Irie T, Uekama K, Manako T, Yano T et al.
The Journal of pharmacy and pharmacology, 1992
→
Inhibitory effect of prostaglandin E1 on laurate-induced peripheral vascular occlusive sequelae in rabbits: optimized topical formulation with beta-cy
Adachi H, Irie T, Uekama K, Manako T, Yano T et al.
The Journal of pharmacy and pharmacology, 1992
→
Contact allergy related to TEA-PEG-3 cocamide sulfate and cocamidopropyl betaine in a shampoo.
Andersen KE, Roed-Petersen J, Kamp P
Contact dermatitis, 1984
→
Contact allergy related to TEA-PEG-3 cocamide sulfate and cocamidopropyl betaine in a shampoo.
Andersen KE, Roed-Petersen J, Kamp P
Contact dermatitis, 1984
→
Allergic contact dermatitis to coco betaine in a beard cleanser.
Badaoui A
Contact dermatitis, 2024
→
Allergic contact dermatitis to coco betaine in a beard cleanser.
Badaoui A
Contact dermatitis, 2024
→
Safety Assessment of Tetrasodium Glutamate Diacetate and Beta-Alanine Diacetic Acid as Used in Cosmetics.
Burnett CL, Bergfeld WF, Belsito DV, Cohen DE, Klaassen CD et al.
International journal of toxicology, 2025
→
Safety Assessment of Tetrasodium Glutamate Diacetate and Beta-Alanine Diacetic Acid as Used in Cosmetics.
Burnett CL, Bergfeld WF, Belsito DV, Cohen DE, Klaassen CD et al.
International journal of toxicology, 2025
→
Final Report of the Cosmetic Ingredient Review Expert Panel on the Safety Assessment of Cocamidopropyl Betaine (CAPB)
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Final Report on the Safety Assessment of Acacia Catechu, Acacia Concinna, Acacia Concinna Extract, Acacia Dealbeta, Acacia Dealbata Extract, Acacia Decurrens, Acacia Decurrens Extract, Acacia Farnesia
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Final Report on the Safety Assessment of Cocamidopropyl Betaine
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Safety Assessment of Alkyl Betaines as Used in Cosmetics
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Safety Assessment of Tetrasodium Glutamate Diacetate and Beta-Alanine Diacetic Acid as Used in Cosmetics
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Almondamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Apricotamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Avocadamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Babassuamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Behenamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Behenyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Beta vulgaris (beetroot) extract
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Beta-Alanine Diacetic Acid
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Beta-Caryophyllene
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Beta-Glucan Hydroxypropyltrimonium Chloride
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Beta-Glucan Palmitate
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Beta-Sitosteryl Acetate
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Betaphycus Gelatinum Extract
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Canolamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Capryl/Capramidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Cetyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Cocamidopropyl Betainamide MEA Chloride
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Cocamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Coco-Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Coco/Oleamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Coco/Sunfloweramidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Cupuassuamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Cystine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Decyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Dipalmitoyl Cystine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Hydrogenated Tallow Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Hydrolyzed Beta-Glucan
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Isostearamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Lauramidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Lauryl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Meadowfoamamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Methacryloyl Ethyl Betaine/Acrylates Copolymer
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Milkamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Minkamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Myristamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Myristyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Oatamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Oleamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Oleyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Olivamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Oxidized Beta-Glucan
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Palm Kernelamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Palmamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Palmitamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Ricinoleamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Sesamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Shea Butteramidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Sodium Carboxymethyl Beta-Glucan
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Soyamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Stearamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Stearyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Tallow Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Tallowamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Undecylenamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Wheat Germamidopropyl Betaine
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Antifungal Mechanism of Action of Lauryl Betaine Against Skin-Associated Fungus Malassezia restricta.
Do E, Lee HG, Park M, Cho YJ, Kim DH et al.
Mycobiology, 2019
→
8'-Apo-Beta-Carotenal
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Babassuamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Beta Carotene
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Beta Sitosterol
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Beta-Caryophyllene
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Betaphycus Gelatinum Extract
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Capryl/Capramidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Cetyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Cocamidopropyl Betainamide MEA Chloride
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Cocamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Coco-Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Hydrolyzed Beta-Glucan
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Lauramidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Lauryl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Meadowfoamamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Methacryloyl Ethyl Betaine/Acrylates Copolymer
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Myristamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Myristyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Oleamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Oleyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Olivamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Shea Butteramidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Sodium Carboxymethyl Beta-Glucan
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Soyamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Undecylenamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Wheat Germamidopropyl Betaine
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Impact of Salix mucronata bark and betaine as natural alleviators on semen quality, serum biochemistry, and oxidative capacity in heat-stressed rabbit
Farag MFM, Daader AH, El-Darawany AA, Bahgat LB, Al-Marakby KM
Tropical animal health and production, 2025
→
Clobetasone
Health Canada
Health Canada Cosmetic Ingredient Hotlist
→
Safety assessment of cocamidopropyl betaine, a cosmetic ingredient.
Kim D, Seok JK, Kim M, Choi S, Hong J et al.
Toxicological research, 2024
→
Mannitol Is a Good Anticaking Agent for Spray-Dried Hydroxypropyl-Beta-Cyclodextrin Microcapsules.
Kou X, Zhang X, Cheng Y, Yu M, Meng Q et al.
Molecules (Basel, Switzerland), 2023
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Surfactant Penetration into Human Skin from Sodium Dodecyl Sulfate and Lauramidopropyl Betaine Mixtures.
Morris SAV, Xu L, Ananthapadmanabhan KP, Kasting GB
Langmuir : the ACS journal of surfaces and colloids, 2021
→
Safety of alpha-arbutin and beta-arbutin in cosmetic products
Scientific Committee on Consumer Safety (SCCS)
European Commission — SCCS
→
Human beta-defensin-2.
Schröder JM, Harder J
The international journal of biochemistry & cell biology, 1999
→
Chitosan/β-glucan/cystine multifunctional hydrogel loading retinol liposomes for efficiently treating UV-induced skin damage and aging.
Song Q, Wang Y, Tan Z, Xiang H, Liu Q et al.
Carbohydrate polymers, 2026
→
Occupational contact allergy to cocamidopropyl betaine and its impurities.
Suuronen K, Pesonen M, Aalto-Korte K
Contact dermatitis, 2012
→
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR