Glutathione is commonly used in Asia as a dietary supplement to lighten skin colour. [5] But how strong is the evidence, and does it differ between capsules and creams? This guide summarises the human studies of glutathione for skin, for formulators and brand owners.
How glutathione may work for skin brightening
Skin colour depends on melanin. Cells make two types: dark eumelanin and lighter pheomelanin. One proposed mechanism is that glutathione shifts production towards pheomelanin, which gives a lighter result. [1] Glutathione is also a powerful antioxidant that neutralises free radicals and helps cells detoxify, and UV exposure creates oxidative stress in skin.
Oral glutathione for skin: the trials
- 500 mg a day for 4 weeks. In 60 healthy medical students in Thailand, the melanin index fell at all six sites measured. The fall was significantly greater than placebo at two sites: the face and the sun-exposed forearm. [2]
- 250 mg a day for 12 weeks. In healthy women, reduced or oxidised glutathione tended to lower the melanin index and UV spots versus placebo. Reduced glutathione lowered wrinkles at some sites. [3]
- Combination with L-cystine. In 124 Asian women over 12 weeks, 500 mg L-cystine plus 250 mg glutathione lightened skin and reduced dark spots. It did better than either ingredient alone or placebo. The authors worked for the producer. [1]
What the reviews conclude
A 2025 systematic review found five randomised trials of oral glutathione at 250 to 500 mg a day. All showed a significant fall in the melanin index versus placebo. The effects did not last after stopping, and topical plus oral glutathione worked better than either alone. [4]
An earlier 2019 review was more cautious. It called the evidence inconclusive because of study quality and inconsistent findings, but saw a trend towards lighter skin in sun-exposed areas. [5]
Topical glutathione
In creams and lotions, the 2025 review found 0.5% glutathione was significantly more effective than 0.1% or placebo. [4] The 2019 review included a 2% oxidised glutathione lotion that lowered the melanin index in sun-exposed skin. [5] The review notes that topical effects are localised, while oral effects are generalised. [4]
For topical brightening formulas, glutathione is often combined with other actives such as alpha arbutin or kojic acid.
Glutathione IV and injections for skin lightening
Glutathione drips and glutathione injection packages are offered for skin whitening in some clinics. The 2025 review found only one placebo-controlled study, with no significant difference from placebo. It concluded that IV glutathione is contraindicated because of a lack of efficacy and its side effects. [4] See glutathione side effects and safety.
How much glutathione per day?
The oral skin trials used 250 to 500 mg a day of glutathione, taken by mouth, for example as a capsule. [2][3][4] The 12-week combination trial used 250 mg glutathione with 500 mg L-cystine. [1] Effects appeared over 4 to 12 weeks of consistent use and faded after stopping. [4]
Can glutathione remove a tan?
The trials measured the melanin index, not tans as such. Effects were clearer in sun-exposed skin, such as the face and forearm, than in sun-protected skin. [2][5] Sun protection remains the main way to prevent tanning. A dermatologist can advise on persistent pigmentation such as melasma.
Claims and regulation
Skin-lightening claims for supplements and cosmetics are regulated. The product category also differs between markets. Before launch, confirm the permitted claims and category for your market, including with NPRA in Malaysia. Describe research on the ingredient, not promises for the finished product.
Formulating a glutathione skin supplement
- Dose. Trials used 250 to 500 mg a day of glutathione.
- Partners. Vitamin C is a common partner, and L-cystine was studied in combination. [1] NAC is a cysteine source for the body’s own glutathione.
- Format. Capsules, tablets, sachets and effervescent tablets are common. Protect powders from moisture during filling.
- Form. Reduced glutathione has the most data. Oxidised glutathione was also studied for skin. [3] See our glutathione forms guide.
What the research says
- In a 12-week double-blind trial in 124 Asian women, 500 mg L-cystine plus 250 mg L-glutathione a day lightened skin and reduced dark spots more than either ingredient alone or placebo. The authors worked for the producer. [1]
- In a 4-week double-blind trial in 60 adults, 500 mg a day lowered the melanin index more than placebo on the face and sun-exposed forearm. [2]
- A 2025 systematic review found oral glutathione at 250–500 mg a day lowered the melanin index versus placebo in five randomised trials, without lasting effect after stopping. Topical 0.5% outperformed 0.1% and placebo. [4]
- A 2019 systematic review judged the evidence inconclusive because of study quality, with a trend towards lighter skin in sun-exposed areas. [5]
These summaries describe published research on the ingredient. They are not claims for any finished product; claims on finished products must meet the rules of the market where they are sold.
References
- Duperray J, et al. The effects of the oral supplementation of L-cystine associated with reduced L-glutathione-GSH on human skin pigmentation: a randomized, double-blinded, benchmark- and placebo-controlled clinical trial. J Cosmet Dermatol. 2022;21(2):802-813. doi:10.1111/jocd.14137
- Arjinpathana N, Asawanonda P. Glutathione as an oral whitening agent: a randomized, double-blind, placebo-controlled study. J Dermatolog Treat. 2012;23(2):97-102. doi:10.3109/09546631003801619
- Weschawalit S, et al. Glutathione and its antiaging and antimelanogenic effects. Clin Cosmet Investig Dermatol. 2017;10:147-153. doi:10.2147/CCID.S128339
- Sarkar R, et al. Glutathione as a skin-lightening agent and in melasma: a systematic review. Int J Dermatol. 2025;64(6):992-1004. doi:10.1111/ijd.17535
- Dilokthornsakul W, et al. The clinical effect of glutathione on skin color and other related skin conditions: a systematic review. J Cosmet Dermatol. 2019;18(3):728-737. doi:10.1111/jocd.12910
Developing a glutathione skin product?
FC Materials supplies L-glutathione reduced (N.L.T 98% assay) to supplement and cosmetic manufacturers in Malaysia, with a lot-specific COA and Halal certificate.
