Glutathione

Topical glutathione (a tripeptide antioxidant/brightening agent) is typically used at low percentages and is generally well-tolerated, with patch-test/consumer data suggesting low rates of irritation compared with stronger actives. However, in compromised skin (e.g., eczema or post-procedure), thiol-containing compounds can still sting or provoke irritant reactions depending on vehicle, pH, and co-ingredients, so it cannot be considered exceptionally gentle/inert. I score it as gentle to reflect low inherent irritancy but non-zero risk in highly reactive patients and in multi-active routines. Safety Notes: In consumer skincare, glutathione (reduced/oxidized forms or liposomal derivatives) is often used at low supportive levels around 0.01–0.1% in brightening serums/creams and in rinse-off cleansers where deposition is limited. Most leave-on brightening products cluster around ~0.1–1% due to cost, odor, and oxidation/stability constraints, while a smaller set of high-strength OTC “glutathione” serums/ampoules marketed for tone improvement reach ~2–5% using anhydrous, encapsulated, or airless packaging to mitigate instability. Higher levels than ~5% are uncommon in true topical formulas because solubility and rapid oxidation significantly limit practical performance, and many products marketed as high-dose may refer to blends/complexes rather than pure glutathione.