Since 1947 Free Form Non-GMO Gluten, Wheat & Dairy Free Suitable for Vegans Certified Gluten Free Kosher Parve Dietary SupplementL-Cysteine is a sulfur-containing amino acid that helps synthesize keratin, a protein found in skin, hair and nails. It is also a precursor to L-Glutathione, a tripeptide involved in one of the body's detoxification systems. This product provides Free Form L-Cysteine to promote optimal absorption and assimilation.