Free Form. Gluten Wheat & Dairy Free. Suitable for Vegetarians. Kosher. L-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.