keratin

noun

ker·​a·​tin ˈker-ə-tən 

: any of various sulfur-containing, fibrous, acidic or basic proteins chiefly of epithelial cells and tissues that are relatively insoluble and resistant to degradation, form filaments which assemble into bundles to provide structural support, and are the primary component of hair, nails, horns, claws, hooves, quills, scales, feathers and the epidermal layer of skin

Note: In addition to its structural properties, keratin also plays a role in cell growth and proliferation, cellular transport of substances, and intercellular communication.

Rhino horn is not actually horn but densely compacted fibers of keratin, a protein found in hair and fingernails.

—Maryanne Vollers

Wool fibers are composed of keratin proteins bundled into microfibrils.

—A. Goho

compare keratinocyte

keratinous

kə-ˈra-tə-nəs 

adjective

Example Sentences

Recent Examples on the Web

Collagen supplements are often recommended for hair growth because collagen has many of the amino acids found in keratin, which is the primary protein found in hair. —Sarah Anzlovar Ms, Health, 17 Mar. 2023

This formula relies on flaxseed and perilla seed oils to strengthen keratin, as well as skin-softening apricot seed oil to keep fingers in tip-top shape, and earned our coveted Best of Beauty Award in 2018. —Alexis Rhiannon, Allure, 16 Mar. 2023

The shampoo and conditioner set features Karmatin, which is essentially a vegan keratin treatment that bonds to hair follicles and remains attached to strands even after rinsing. —Nicol Natale, Peoplemag, 10 Mar. 2023

Or, opt for a product with allantoin, which Dr. Brazzo says can hydrate the skin, soften keratin, and promote healing. —Sarah Bradley, Verywell Health, 6 Mar. 2023

Fendi, for whom fur is still a significant part of the business, has been experimenting with a new alternative using keratin, the main protein in hair. —Nick Haramis Robbie Lawrence Hisato Tasaka, New York Times, 1 Mar. 2023

This Amazon bestseller features natural oils, including coconut oil, as well as vitamins, biotin, and keratin that thoroughly cleanse the scalp to create a clean slate for new growth to sprout. —Nerisha Penrose, ELLE, 28 Feb. 2023

This one contains keratin and hydrating oils that repairs and nourishes your tired, depleted strands. —ELLE, 23 June 2022

What happens is that the hair follicles on your body—especially around backs of the arms, thighs, buttocks, and even face—get plugged up with too much keratin or protein, and turn into small, hard bumps. —Talia Abbas, Glamour, 19 July 2021

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Word History

Etymology

borrowed from German Keratin, from Greek kerat-, stem of kéras "horn" + German -in -in entry 1 — more at kerato-

Note: The term was introduced by the German physician and chemist Johann Franz Simon (1807-43) in Handbuch der angewandten medizinischen Chemie, 1. Theil, Medizinisch-analytische Chemie (Berlin, 1840), p. 49.

First Known Use

circa 1849, in the meaning defined above

Kids Definition

keratin

noun

ker·​a·​tin ˈker-ət-ᵊn 

: a sulfur-containing protein that makes up hair and horny tissues (as nails)

Medical Definition

keratin

noun

ker·​a·​tin ˈker-ət-ən 

: any of various sulfur-containing fibrous proteins that form the chemical basis of horny epidermal tissues (as hair and nails) and are typically not digested by enzymes of the gastrointestinal tract see pseudokeratin