Keratin

protein
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Keratin is a group of structural proteins known for being tough and insoluble. It is the main component of the outermost layer of human skin, hair, and nails, as well as various animal structures such as feathers, hooves, and horns. Its composition is rich in sulfur-containing amino acids such as cysteine, which form strong disulfide bonds that contribute to its stability and resistance to degradation. This protein helps maintain the integrity and protective barrier of different tissues. In the skin, keratinocytes produce keratin to form a shield against environmental damage, pathogens, and moisture loss. For hair, keratin supports strength, elasticity, and shape, while in nails, it forms the hard plate that protects the fingertips and toes. Supplements, often derived from animal sources, are used to support natural keratin production for the health and appearance of hair, skin, and nails. These are frequently hydrolyzed into smaller peptides to support better absorption when taken orally, or applied topically to reinforce external structures.

Natural sources
Human hair, skin, and nails (endogenous production)Animal sources: Feathers, wool, hooves, horns (used for supplements after processing)Foods rich in protein and sulfur-containing amino acids (e.g., eggs, fish, poultry, legumes) which support the body's natural keratin production.

Ingredient forms

No public comparison lists found.

Safety & Toxicity
3 safety notes
  • Individuals with known allergies to animal-derived proteins should use caution.
  • Pregnant or breastfeeding women, and individuals with underlying health conditions, should consult a healthcare professional before taking keratin supplements.
  • Always adhere to recommended dosages for oral supplements.
Goals
Hair Health
Hair Health
Impact
High effect
Typical dose:250–500 mg
Since hair is composed of about 95% keratin, supplementing with a bioavailable form (e.g., solubilized keratin) provides the body with the exact material needed for hair structure. Clinical studies on specific forms have demonstrated a significant reduction in hair shedding and an improvement in hair brightness and strength.

Study evidence

14 studies

Keratin supplements have limited evidence for improving hair appearance, while broader effects on growth or shedding remain uncertain. Some favorable findings involve added vitamins and minerals, and cosmetic hair coatings or fillers do not demonstrate benefits from taking keratin orally.

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Nail Health
Nail Health
Impact
High effect
Typical dose:250–1000 mg
Supplementing with solubilized keratin provides the complete profile of amino acids, including the sulfur-containing ones like cysteine, in the exact form used by the body to build nails. This can help improve nail hardness, smoothness, and reduce breakage.

Study evidence

7 studies

Keratin supplements show preliminary promise for improving nail hardness and appearance, but the evidence concerns specific products studied in women. Some products also contain vitamins and minerals, so the contribution of Keratin alone and its broader effects on nail health remain uncertain.

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Studies

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Interactions

Positive Interactions

Biotin
Biotin is essential for the body's keratin infrastructure and promotes healthy hair and nail growth, working synergistically with keratin.
Cysteine
Cysteine is a crucial sulfur-containing amino acid and a primary building block of keratin, directly supporting its synthesis and structure.
METHIONINE
Methionine is another essential sulfur-containing amino acid vital for keratin synthesis and overall hair health.
Silicon
Silicon contributes to the structural integrity of hair, skin, and nails, enhancing the benefits of keratin for strength and resilience.
Vitamin C
Vitamin C is essential for collagen synthesis, which supports the dermal layer and hair follicles where keratin is produced.
Zinc
Zinc plays a vital role in protein synthesis and cell division, which are crucial for the growth and repair of keratin-rich tissues.
Copper
Copper is involved in collagen formation and hair pigmentation, supporting healthy hair structure alongside keratin.
Collagen
Collagen provides structural support to skin and connective tissues, working synergistically with keratin for overall skin, hair, and nail health.
Horsetail
Horsetail is a natural source of silicon, which can enhance keratin's benefits for hair and nails by improving their strength.
Glutathione
Glutathione, a powerful antioxidant, can protect cells, including keratinocytes, from oxidative stress, supporting overall tissue health and keratin integrity.
Vitamin A
Vitamin A supports cell growth and differentiation, important for healthy skin and hair follicle function where keratin is produced.
Vitamin E
Vitamin E is an antioxidant that can help protect cells from damage, supporting the health of keratin-producing cells and the scalp.
Folate
Folate is involved in cell division and tissue growth, contributing to healthy hair and skin, and thus supporting keratin-rich tissues.
Iron
Iron is essential for oxygen transport to hair follicles, supporting their healthy function and efficient keratin production.
Proline
Proline, an amino acid, is a major component of collagen, which supports the dermal layers where keratin structures are formed.
Glycine
Glycine, another amino acid crucial for collagen structure, indirectly supports the environment for keratin production.
Lysine
Lysine is an essential amino acid involved in protein synthesis and collagen formation, which supports tissues containing keratin.
Vitamin B6
Vitamin B6 acts as a cofactor in amino acid metabolism, including those essential for keratin synthesis.
Vitamin B5
Vitamin B5 (Pantothenic Acid) is known to support hair strength and elasticity, complementing keratin's role.
Hyaluronic Acid
Hyaluronic Acid hydrates and provides structural support to the skin, complementing keratin's barrier function and promoting skin health.

Negative Interactions

N/A
No known direct negative interactions with other ingredients on the provided list.
Sources

Up to five highest-ranked published examples per goal. Study counts and charts include all published studies for the connection.

  1. The Effects of an Oral Supplementation of a Natural Keratin Hydrolysate on Skin Aging: A Randomized, Double-Blind, Placebo-Controlled Clinical Study in Healthy Women.
    Tursi F; Nobile V; Cestone E; De Ponti I; Lepoudere A; Sergheraert R; Soulard JP · Journal of cosmetic dermatology · 2025
    Randomized trialHair HealthNail Health
  2. Halloysite/Keratin Nanocomposite for Human Hair Photoprotection Coating.
    Cavallaro G; Milioto S; Konnova S; Fakhrullina G; Akhatova F; Lazzara G; Fakhrullin R; Lvov Y · ACS applied materials & interfaces · 2021
    In vitro / ex vivo studyHair Health
  3. Annurca Apple Nutraceutical Formulation Enhances Keratin Expression in a Human Model of Skin and Promotes Hair Growth and Tropism in a Randomized Clinical Trial.
    Tenore GC; Caruso D; Buonomo G; D'Avino M; Santamaria R; Irace C; Piccolo M; Maisto M; Novellino E · Journal of medicinal food · 2018
    Randomized trialHair Health
  4. Keratin/alginate hybrid hydrogels filled with halloysite clay nanotubes for protective treatment of human hair.
    Cavallaro G; Caruso MR; Milioto S; Fakhrullin R; Lazzara G · International journal of biological macromolecules · 2022
    In vitro / ex vivo studyHair Health
  5. Patient Satisfaction and Adverse Effects Following the use of Topical Hair Fiber Fillers.
    Babadjouni A; Juhasz M; Pham C; Csuka E; Hedayati B; Evron E; Mesinkovska NA · International journal of trichology · 2024
    Cross-sectional study40 participantsHair Health
  6. Comparative Analysis of Type I Keratin Expression By Nail Consistency: An Immunohistochemistry Study.
    Mingorance Álvarez E; Rodríguez-León J; Pérez Pico AM; Mayordomo R · Applied immunohistochemistry & molecular morphology : AIMM · 2022
    Cross-sectional study32 participantsNail Health
  7. Exposure to toxic agents alters organic elemental composition in human fingernails.
    Schumacher E; Dindorf W; Dittmar M · The Science of the total environment · 2009
    Cross-sectional study120 participantsNail Health
  8. Human keratin diseases: hereditary fragility of specific epithelial tissues.
    Corden LD; McLean WH · Experimental dermatology · 1997
    Narrative reviewNail Health
  9. Phenotype and genotype features of Vietnamese children with pachyonychia congenita.
    Chu HT; Dinh Duong TA; Le DH; Le TV; Nguyen BB; Dang CV; Vu QV · Pediatrics and neonatology · 2023
    Case series7 participantsNail Health