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Antioxidants

Glutathione

Also listed as L-glutathione

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.

Weak evidenceTypical strength: About 2% in the key trial

What it is

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.

How strong is the evidence?

Weak evidence

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.

What it's used for, checked

Brightening and dark spots

Mixed

One small placebo-controlled trial found a lower melanin index at 10 weeks; not independently replicated.

Antioxidant protection

Unproven

Plausible from its biology, but not shown for topical products.

IV or injected skin whitening

Unproven

No evidence it works, and adverse effects have prompted a public warning from a national drug regulator.

Who should be careful

  • Topical glutathione is generally well tolerated.
  • Avoid intravenous glutathione drips for skin lightening: no proven benefit and reported serious adverse effects.

The studies

Every citation is checked against its PubMed record.

  1. Skin-whitening and skin-condition-improving effects of topical oxidized glutathione: a double-blind and placebo-controlled clinical trial in healthy women.
    Watanabe F, Hashizume E, Chan GP, Kamimura A · Clinical, Cosmetic and Investigational Dermatology · 2014 · RCT (split-face)

    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.

  2. Glutathione as a skin whitening agent: Facts, myths, evidence and controversies.
    Sonthalia S, Daulatabad D, Sarkar R · Indian Journal of Dermatology, Venereology and Leprology · 2016 · Review

    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.