The primary component of human hair is a protein called keratin. Keratin is a fibrous structural protein that provides strength, durability, and protection to hair, skin, and nails. It consists of long chains of amino acids, which form its unique helical structure. There are two main types of keratin found in hair: alpha-keratin and beta-keratin. Besides providing structural stability, keratin also plays a role in moisture retention, making it an important factor in hair health and appearance.