April 2024 in “Current research in nutrition and food science” Taking an amino acid supplement improved skin, hair, and nail health in women.
1 citations
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January 1996 Cysteine and arginine are essential for hair growth and thickness.
9 citations
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August 2007 in “Journal of animal science/Journal of animal science ... and ASAS reference compendium” Sheep wool follicles absorb different amino acids at various rates and locations, which could affect wool growth based on diet and genetics.
December 2025 in “Universal library of medical and health sciences.” Amino acids like arginine and cysteine protect hair during chemical treatments, keeping it strong and less brittle.
5 citations
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October 2007 in “PubMed” Amino acids in conditioners improve hair strength, hydration, and color retention.
12 citations
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July 2017 in “International Journal of Cosmetic Science” N‐AOHPA is a promising alternative to traditional surfactants for better hair conditioning.
1 citations
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January 1998 in “Cosmetics and toiletries” Both amodimethicone and dimethicone copolyol amine are effective hair conditioners.
7 citations
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January 1982 in “Acta agriculturae Scandinavica” Mink use L-methionine and L-cystine slightly better than natural amino acids for hair growth, but D-methionine is not effective.
May 2026 in “Fibers and Polymers” 76 citations
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December 2011 in “Journal of Cell Science” Different keratin types have unique amino acid patterns that are evolutionarily conserved.
5 citations
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May 1983 in “Australian journal of biological sciences” Certain amino acid analogues can inhibit wool and hair growth and affect fiber strength.
4 citations
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December 1989 in “The Journal of Dermatology” Human hair proteins have similar cysteine and glycine levels to skin proteins.
February 2025 in “International Journal of Cosmetic Science” A new amino acid derivative, ATS, improves hair texture and moisture, making it easier to straighten curly hair.
7 citations
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January 1959 in “Canadian Journal of Chemistry” Human and horse hair have similar end groups to wool and feathers.
15 citations
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October 1970 in “Archives of disease in childhood” Hair amino acid levels can indicate metabolic disorders.
March 1990 in “Journal of Dermatological Science” 125 citations
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February 1971 in “Biochemistry” Specific cross-linkages help make hair proteins stable and strong.
4 citations
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December 2018 in “Macedonian Journal of Chemistry and Chemical Engineering” A new method accurately measures amino acids in treated hair, showing bleaching reduces amino acids while protein treatments increase them.
49 citations
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January 1972 in “Biochimica et Biophysica Acta (BBA) - Protein Structure” March 2005 in “Journal of the American Academy of Dermatology” Adding amino acids to damaged hair can improve its strength and appearance.
January 1974 in “Nippon Nōgei Kagakukaishi/Nihon Nougei Kagakkaishi” Applying L-methionine and L-serine to the skin promotes the most hair growth.
November 2023 in “BMC genomics” The study concluded that the arachidonic acid pathway and the protein KRT79 play a role in determining the fineness of cashmere.
52 citations
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May 2006 in “Journal of Structural Biology” Keratin-associated proteins help link filaments and affect keratin's strength.
9 citations
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January 1981 Nucleophilic reagents break down hair keratin, forming more lanthionine and lysinoalanine than in wool.
46 citations
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November 1963 in “Journal of Histochemistry & Cytochemistry” Arginine converts to citrulline in hair follicles as proteins harden.
September 2025 in “Animals” Key proteins and pathways are crucial for wool fineness, but more research is needed.
5 citations
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February 1998 in “Polymer” Human hair keratin has a 40% α-helix structure that changes to a random coil in 8 M urea.
13 citations
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February 2019 in “Zoology” Lustre mutant sheep have normal hair structure and proteins but differ in felting properties.
3 citations
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November 2021 in “Frontiers in Genetics” Certain genes are linked to the quality of cashmere in goats.
42 citations
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February 1996 in “Journal of Investigative Dermatology” Polyamines, especially spermidine, are essential for hair growth.