Thymosin alpha-1 vs Glutathione
A peptide sold by wellness clinics as an immune booster. Trials show a modest effect in hepatitis B, and a large sepsis trial found none. It is sold as an antioxidant booster, for skin lightening drips and for detox. One small trial showed slight lightening at two skin sites, and trials for other uses failed.
Both sit at grade B: some human evidence. Neither is FDA approved.
Evidence
BSome human evidence
BSome human evidence
Human studies cited
Animal or cell studies cited
Why the grade
Thymosin alpha-1 has several randomized trials in chronic hepatitis B (98 and 316 patients) and a meta-analysis of five trials with 353 patients showing delayed viral suppression, which is the approved use abroad. The 1,106-patient TESTS phase 3 trial in sepsis found no mortality benefit. The general immune-boosting use it is sold for in the US has no controlled trials, so the compound grades B on its hepatitis B evidence and D on the wellness claims.
For skin lightening, the use glutathione is most often sold for, there is one randomised placebo-controlled trial of oral glutathione in 60 healthy students that found a small drop in melanin index at two of six skin sites. The larger trials in hand were for other purposes: a 153-patient inhaled trial in cystic fibrosis that missed its primary endpoint, a 54-adult trial showing oral glutathione raises blood levels, and a 21-patient Parkinson's pilot. No trial of intravenous glutathione for skin exists.
FDA
Not approved
Thymosin alpha-1 is not approved by the FDA for any use. It is approved as thymalfasin (Zadaxin) in more than 35 other countries for hepatitis B and C and as an immune adjuvant. In the United States it was taken off the FDA's Category 2 compounding list after its nominators withdrew it, and in December 2024 the Pharmacy Compounding Advisory Committee voted 17 to 4 against adding it to the 503A bulks list; it is sold online as a research chemical.
Not approved
Glutathione is not approved by the FDA as a drug for any indication. Oral glutathione is sold as a dietary supplement, intravenous and inhaled forms are made by compounding pharmacies, and glutathione sits in Category 1 of the FDA's list of nominated compounding substances, meaning it may be compounded while the agency evaluates it. In August 2026 the agency warned compounders not to use supplement grade glutathione in injectables after a cluster of adverse events.
Sold for
Thymosin alpha-1 is sold by wellness clinics as an immune-system booster for infections, cancer support, autoimmune disease and long COVID.
Glutathione is sold as a master antioxidant, for skin whitening by intravenous drip, for detox and for Parkinson's disease.
Studies say
Randomized trials support a modest, delayed antiviral effect in chronic hepatitis B, a large trial found no benefit in sepsis, and there are no trials of the immune-boosting uses marketed in the US, which is why it grades B.
Oral glutathione does raise body stores and produced a modest, site-specific lightening in one small trial, while inhaled glutathione failed in cystic fibrosis and intravenous glutathione showed no clear benefit in a Parkinson's pilot, so the grade is B for the skin claim and lower for the others.
Class
Immunomodulatory peptide
Antioxidant tripeptide
Route
Injection
Several routes