Glutathione is an antioxidant produced in cells. It’s comprised largely of three amino acids: glutamine, glycine, and cysteine. Glutathione levels in the body may be reduced by a number of factors, including poor nutrition, environmental toxins, and stress. Its levels also decline with age. In addition to being produced naturally by the body, glutathione can be given intravenously, topically, or as an inhalant. It’s also available as an oral supplement in capsule and liquid form.