N-acetyl cysteine (NAC) is a stable form of the non-essential amino acid cysteine. It is a sulfur-containing amino acid that acts as a stabilizer for the formation of protein structures and is also necessary for the formation of glutathione. Molybdenum and selenium are essential trace minerals that facilitate the production of several important enzymes. Take 1 capsule twice daily. Black speckling may occur over time after package is opened, but product is safe to consume. NAC is a sulfur-containing amino acid, so an unpleasant smell is possible. Leave dessicant and charcoal packets in bottle after opening to delay oxidation and control odor (if any). Other Ingredients: Hypromellose (cellulose capsule), Stearic Acid (vegetable source) and Citric Acid.