Glutathione

What is glutathione?

Glutathione is a tripeptide of cysteine, glutamate and glycine, and the body's principal intracellular antioxidant. Its pigmentation interest comes from a real mechanism: it shifts melanin synthesis from darker eumelanin toward lighter pheomelanin and inhibits tyrosinase indirectly.

Three different questions

Intravenous glutathione for skin lightening is widely marketed and poorly evidenced, and has attracted safety warnings from regulators in several countries. It is not a cosmetic proposition and should not be discussed as one.

Oral glutathione faces a bioavailability problem - it is largely broken down in the gut, and evidence for skin effects is thin.

Topical glutathione is the only version relevant to a cosmetic product, and here the honest position is that the molecule is hydrophilic, unstable and around 307 daltons, so delivery is a genuine challenge, and the clinical evidence for topical glutathione specifically is limited. Some work on oxidised glutathione and on delivery-enhanced forms is more encouraging.

Reduced or oxidised · the label rarely says

Two forms are used and they are not interchangeable. Reduced glutathione (GSH) is the form active inside cells, and the one that oxidises readily in a jar. Oxidised glutathione (GSSG) is considerably more stable, and it is the form carrying the better topical evidence: a double-blind, placebo-controlled split-face trial in 30 women found 2% GSSG lotion produced measurable lightening and skin-condition improvement against placebo on the opposite side of the face over ten weeks. That trial was run by the ingredient's manufacturer, which is worth knowing, but it remains the strongest topical result available.

Concentration matters too. A 2025 systematic review found 0.5% topical glutathione outperformed both 0.1% and placebo - so a product listing glutathione without stating the form or the level has told you very little.

How to present it

As a supporting antioxidant with a plausible pigmentation mechanism and limited topical evidence - not as a lightening agent. Vegalab includes it in the Brightening line alongside tranexamic acid, niacinamide, alpha-arbutin and mandelic acid, all of which have stronger individual evidence. That is a reasonable place for it: contributing to a multi-pathway formula rather than carrying the claim.

What does glutathione not do?

It does not lighten overall skin tone in any way supported by good topical evidence, and any product implying it does is overreaching. It is also unstable in aqueous formulation, so stability data matters.