Definitions

1. noun

a type of protein found in the skin, hair, and nails of humans and animals, making up the outer layer of the skin and the hard structures of hair and nails.

“The dermatologist said that the new skin treatment was based on the properties of keratin.”

2. noun

a hard, protein-based material used in the manufacture of combs, brushes, and other cosmetic products.

“The hair salon used a keratin-based comb to style the client’s hair.”