Keratin Amino Acids are a low-molecular-weight mixture of amino acids derived from the complete hydrolysis of keratin. This ingredient penetrates the hair cuticle and skin’s stratum corneum more effectively than hydrolyzed proteins to provide moisture retention and structural reinforcement.
- INCI Name:
- Keratin Amino Acids
- Chemical/Scientific Name:
- Amino acids, keratin-derived
- Common Aliases:
- Cysteine, arginine, and lysine complex; hydrolyzed keratin peptides
| Category: | Softeners |
| Source Origin: | Animal-derived (typically sheep wool) or Synthetic |
| Comedogenic Rating: | 0 |
| Primary Industries: | Hair Care, Skin Care, Nail Care |
| Solubility: | Water-soluble |
At a Glance: Properties & Effects
| Hydration/Moisture | |
| Barrier Repair | |
| Texture Enhancement | |
| Irritation Risk |
- Primary Benefits:
- Deeply hydrates the hair shaft to improve elasticity and reduce breakage.
- Functions as a Natural Moisturizing Factor (NMF) component in the skin to prevent transepidermal water loss.
- Strengthens brittle nails by reinforcing the disulfide bonds within the nail plate.
- Smooths the hair cuticle for increased shine and manageability without heavy buildup.
- Potential Risks:
- Potential for “protein overload” in low-porosity hair if used excessively, leading to stiffness.
- Ethical concerns for vegan consumers as it is predominantly sourced from wool.
Biological Action & Cosmetic Profile
Keratin Amino Acids function as the fundamental building blocks of the fibrous structural proteins found in hair, skin, and nails. Unlike hydrolyzed-keratin, which consists of larger protein fragments, these amino acids are fully hydrolyzed, resulting in a molecular weight small enough to pass through the cuticle and reach the cortex of the hair. This penetration allows for the internal re-hydration of the hair fiber, effectively replacing the moisture lost during chemical processing or heat styling.
Dermatological application relies on the specific profile of amino acids present, which often includes high concentrations of proline, serine, threonine, glycine, alanine, and isoleucine. These molecules act as humectants that bind water to the stratum corneum, mimicking the skin’s natural moisturizing factors. Because these amino acids are chemically similar to the skin’s own composition, they exhibit high biocompatibility and support the integrity of the acid mantle.
Sulfur-containing amino acids within the mixture, specifically cysteine, are critical for forming disulfide bridges. These bridges provide the physical strength and resilience associated with healthy keratinized tissues. In nail care formulations, the topical application of these amino acids helps repair damage caused by detergents and environmental stressors by filling micro-fissures in the nail plate.
Broader Applications & Origins
Sourcing for this ingredient almost exclusively involves the hydrolysis of keratinous materials such as sheep’s wool, feathers, or horns. The extraction process uses enzymes or acids to break the protein chains down into individual amino acids or very short peptide chains. While synthetic versions exist, the complex ratio of amino acids found in natural keratin is difficult to replicate, making animal-derived versions the industry standard.
Technological advancements in green chemistry have enabled more sustainable extraction methods that preserve the bioactivity of the amino acids. In professional salon treatments, these amino acids are often preferred over silicones for “repair” claims because they provide structural benefits rather than just a superficial coating. Beyond cosmetics, similar amino acid profiles are utilized in medical wound care to support tissue regeneration.
Routine Integration
- Synergies:
- Panthenol: Enhances moisture retention and improves hair flexibility when paired with protein building blocks.
- Sodium-pca: Works alongside amino acids to bolster the skin’s Natural Moisturizing Factor (NMF).
- Hyaluronic-acid: Creates a dual-layer hydration system where amino acids penetrate deeply and hyaluronic acid hydrates the surface.
Clinical Consensus & Safety
The Cosmetic Ingredient Review (CIR) Expert Panel has evaluated Keratin Amino Acids and concluded they are safe for use in cosmetic products. Since these amino acids are naturally occurring components of the human body, they possess a very low sensitization potential and are generally non-irritating even at high concentrations. Regulatory bodies like CosIng categorize the ingredient as a conditioning agent and humectant, with no specific restrictive limits on concentration in rinse-off or leave-on products. Clinical data suggests that while they provide significant temporary structural improvement to damaged hair, they do not permanently “heal” split ends.
Is this ingredient vegan?
In most cases, no. Keratin Amino Acids are typically derived from sheep’s wool or other animal byproducts. If a product is labeled vegan, the formulator has likely used a “pseudo-keratin” composed of plant-based amino acids from hydrolyzed-wheat-protein or hydrolyzed-soy-protein blended to mimic the keratin profile.
Can it cause hair to become brittle?
Excessive use of any protein-based ingredient, including amino acids, can lead to a condition known as protein-moisture imbalance. This occurs when the hair becomes saturated with structural molecules at the expense of softening lipids, making the hair feel stiff or “crunchy.” Using a moisturizing conditioner alongside protein treatments prevents this issue.
How does it differ from hydrolyzed keratin?
The primary difference is molecular size. Keratin Amino Acids are the smallest possible units, allowing for deep penetration. Hydrolyzed-keratin contains larger peptides that tend to film-form on the surface of the hair or skin, providing more surface smoothing but less internal repair.