CYSTEINE

📋 Quick facts

Description: CYSTEINE — amino acid, part of the skin natural moisturizing factor (NMF), supports keratin structure.

All Functions: amino acid, part of the skin natural moisturizing factor (NMF), supports keratin structure

Quick Facts:

• Category: humectant

Proven Benefits At A Glance:

• Cysteine is an amino acid used in pharmaceuticals, food, cosmetics, and animal feed
• In skin cells, cysteine residues are involved in regulating melanin production through a process called palmitoylation
• Cysteine-based compounds show potential as carriers for delivering topical skincare ingredients to the epidermis
• Cysteine protease inhibitors have been studied for their anti-fibrosis properties in skin tissue

⚗️ Chemical Overview

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. DL-cysteine has been reported in Trifolium repens, Trifolium pratense, and other organisms with data available. See also: L-(+)-Cysteine (annotation moved to).

Source(s): LOTUS – the natural products occurrence database, ChEBI, PubChem, via PubChem

📊 Comedogenicity

🛡️ Safety rating

Safety tier is a starting heuristic from regulatory status and comedogenic rating, not a dermatological verdict — see our Terms for the full disclaimer. Research confidence reflects how many real cited studies back this ingredient, not the strength of their findings.

🌍 Regulatory Status

💧 Skin Type Compatibility

⚠️ Don’t Combine With

📚 Research & Evidence

🔬 The Science

Cysteine is a proteogenic amino acid—meaning it’s one of the building blocks cells use to make proteins (Molecules, 2024). In skincare specifically, research has uncovered an interesting mechanism: cysteine residues on tyrosinase, the enzyme responsible for melanin production, can undergo a chemical modification called palmitoylation (the attachment of a fatty acid called palmitic acid). This modification affects how quickly tyrosinase gets broken down in melanocytes, thereby influencing melanin levels. When this palmitoylation process was blocked experimentally, tyrosinase accumulated and melanin increased; when specific proteins (DHHC2, 3, and 15) that add this modification were reduced, similar increases in tyrosinase and melanin were observed (J Invest Dermatol, 2023).

This suggests cysteine’s chemical properties play a regulatory role in skin pigmentation, though this is a mechanistic finding rather than a direct claim about cysteine itself as an ingredient. Cysteine has also been explored as a structural component of advanced topical delivery systems. #1: When cysteine was chemically linked to other molecules to create specialized carriers called transfersomes, these modified carriers showed enhanced ability to deposit active ingredients specifically in the epidermis (the outermost skin layer) rather than allowing them to penetrate deeper (Molecules, 2023). #2: Additionally, cysteine protease inhibitors—compounds that block enzymes in the cysteine protease family—demonstrated anti-fibrotic effects in research on skin and lung tissue, suppressing the development of excessive collagen deposition in animal models (Arthritis Res Ther, 2023), though this research focused on disease states rather than cosmetic applications.

It’s important to note that these sources describe cysteine’s role in pharmaceutical delivery systems and cellular mechanisms rather than direct skincare benefits from cysteine as a standalone ingredient. The research is mechanistic and largely focused on specialized pharmaceutical or medical applications rather than consumer skincare products.

📄 Related Research

Matched by search — not necessarily verified support for every statement above.

• You J et al. (2021). Cysteine-Based Coupling: Challenges and Solutions. Bioconjug Chem.
• Caballero Cerbon DA et al. (2024). Challenges and Advances in the Bioproduction of L-Cysteine. Molecules.
• Niki Y et al. (2023). S-Palmitoylation of Tyrosinase at Cysteine(500) Regulates Melanogenesis. J Invest Dermatol.
• Kasamatsu H et al. (2023). A cysteine proteinase inhibitor ALLN alleviates bleomycin-induced skin and lung fibrosis. Arthritis Res Ther.
• Niu J et al. (2023). L-Cysteine-Modified Transfersomes for Enhanced Epidermal Delivery of Podophyllotoxin. Molecules.

🧴 Products Containing CYSTEINE

• L’OREAL NORGE AS L’Oreal Lash Serum Transparent
• collagen face mask
• Les Cosmétiques Design Paris, Men’Activ Science Ultra Density Shampooing densifiant antipelliculaire
• ecojeratin
• Barba Forte Condicionador Barba e Cabelo Don Forte Barba Forte 170ml
• REMEDY CALAZIME Skin Protectant Paste
• Herbal time хининов мицеларен шампоан
• ipca Keraglo Men