The body's main internal antioxidant, sold as a skin brightener. Topical evidence is one small company-run trial; IV 'whitening' drips are unproven and risky.
Glutathione is a three-amino-acid peptide every cell makes to neutralize oxidants. It also shifts pigment production away from dark eumelanin, which is behind its reputation as a skin-lightening ingredient.
In skincare it is unstable and oxidizes easily, and how much reaches pigment cells is unclear. In a 10-week split-face trial by an ingredient maker, a 2% oxidized-glutathione lotion lowered the skin's melanin index versus placebo in 30 women. Reviews call the overall evidence thin and the marketing ahead of it.
One randomized, placebo-controlled topical trial (30 women, run by the ingredient's manufacturer) and a few small oral trials support modest lightening. Intravenous glutathione for skin lightening has no proof of efficacy and has drawn regulatory safety warnings. How long any effect lasts is unknown.
30 women applied 2% oxidized glutathione lotion to one side of the face and placebo to the other for 10 weeks; the melanin index fell significantly more on the glutathione side, which also gained hydration and smoothness. Conducted by the ingredient's manufacturer.
Three small randomized trials support modest lightening from topical and oral glutathione; intravenous use has no evidence of efficacy and led the Philippine drug regulator to issue a public warning. Duration and durability of effect are unknown.