Keratin is a form of protein that can be found in epithelial cells making up our nails, skin, and hair. It is responsible for the structure and growth of these body parts. As a protective protein, keratin is less susceptible to tearing and scratching. This provides a barrier of protection and support for the skin, hair, and nails. Keratin can be found in your glands and internal organs as well. The amount of keratin in the body may affect the health of these body parts. People can extract keratin from feathers, wool, and hooves to use for treatments, supplements, and other products that can help with nail, skin, and hair health.