A protein commonly found in human hair, fingernails, and toenails.

Some products include keratin to support healthier skin and hair. Keratin may improve skin elasticity, and it has a waterproofing effect when applied topically. It is also commonly used in hair-straightening treatments.

Keratin is a natural substance that should not cause negative side effects when applied directly to the skin. It is a safe ingredient in personal lubricants and cosmetics.