Acetyl Cysteine Best Antioxidant Anti-Ageing Hydration Acetyl Cysteine description Acetyl cysteine, known also as aceytlcysteine, n-acetylcysteine and NAC, is an ingredient used for years in clinical settings to treat acetaminophen overdose. It is a derivative of the amino acid l-cysteine and is a precursor of the body’s master antioxidant, glutathione. In recent years, scientists have discovered new properties and uses for acetyl cysteine, one of which is its value as an anti-aging ingredient in skin care. As a precursor to glutathione, it also has antioxidant properties and with it, free-radical scavenging abilities that fight premature signs of aging. Acetyl cysteine also showed skin-calming effects and in some studies improved skin hydration via decrease of trans-epidermal water loss. The independent Cosmetic Ingredient Review Expert Panel has ruled acetyl cysteine safe in its current usage and practice in cosmetics. Use levels of acetyl cysteine in cosmetics range from 0.0005-0.1%. Related ingredients: Glutathione L-Cysteine