Glutathione is a three-amino-acid peptide — glutamate, cysteine and glycine — that cells make for themselves and use as their main antioxidant. It is poorly absorbed by mouth, which is why sellers offer it as an injection, an IV drip, a patch and a nasal spray. The nasal spray is the one route with a small, specific human research record, and it is all in one disease.
This page is that record, as a reproducible census. How glutathione by injection compares with capsules is on our glutathione injection vs oral page, and the general case for and against the nose as a route for peptides is on our peptide nasal spray page. Glutathione for skin lightening is a different question, covered by PeptideGlowJournal's glutathione for skin page. Nothing here is a recommendation.
The census
Run on 27 October 2026, so anyone can repeat it:
| Query | Records | Human intranasal glutathione studies |
|---|---|---|
PubMed: glutathione[tiab] AND intranasal[tiab] |
156 | 3 |
| PubMed: the same with "nasal spray", limited to clinical trial or RCT | 4 | 2 |
| ClinicalTrials.gov: "intranasal glutathione" | 6 | 4 (3 completed, 1 recruiting) |
Most of the 156 PubMed records use the two words for other reasons — glutathione measured in nasal tissue, intranasal delivery of a different drug, glutathione as an oxidative-stress marker. Of the four records tagged as trials, two are not glutathione sprays at all: a 2021 trial of broccoli sprout extract in hay fever and a 2013 study of glutathione-enzyme genes in glioma patients given a different nasal drug. That is the usual shape of a supplement's "studies": the count looks larger than the evidence.
The three human studies
All three come from Laurie Mischley's research group in Washington State, all in people with Parkinson's disease, in whom glutathione is depleted early in the disease.
| Study | Design | Participants | What was given | Finding |
|---|---|---|---|---|
| Mischley 2015, Mov Disord (NCT01398748) | Randomised, double-blind, phase I/IIa, 3 months | 30 | Saline, or 300 or 600 mg/day in three divided doses | No substantial differences in adverse events between groups; "all groups met tolerability criteria" |
| Mischley 2016, npj Parkinsons Dis (NCT02324426) | Single dose inside an MR scanner, no control group | 15 | 200 mg once | Brain glutathione above baseline at every time point after 8 minutes, for at least ~1 hour |
| Mischley 2017, J Parkinsons Dis (NCT02424708) | Randomised, double-blind, phase IIb, 3 months + 1-month washout | 45 | Saline, or 100 or 200 mg three times a day | All groups improved, including placebo; neither dose superior to placebo; one cardiomyopathy case in the 200 mg group |
Abstracts and registry records read 27 October 2026. In total, 90 people have taken part in the published human research on glutathione nasal spray, every one of them with Parkinson's.
What the phase IIb trial actually showed
The 2017 trial is the only one designed to look for benefit, and its result is easy to misread. The high-dose group's motor and total symptom scores improved from their own baseline — by 4.6 points on the total Unified Parkinson's Disease Rating Scale — but the saline group improved too, and neither glutathione group did better than saline. The authors' conclusion: the data "do not suggest (in)GSH is superior to placebo after a three month intervention", and the placebo improvement "was more robust than has been observed in previous PD studies".
A product page quoting "improved Parkinson's symptoms" from this trial is quoting the within-group change and leaving out the comparison the trial was built to make.
What the brain-scan study showed, and what it did not
The 2016 study is the reason sellers say glutathione spray "reaches the brain". It measured brain glutathione by magnetic resonance spectroscopy in 15 people, gave 200 mg into the nose without moving them, and scanned repeatedly for about an hour. Glutathione was not raised at 8 minutes and was significantly above baseline at every later time point. That is evidence the spray changed a brain measurement in this group, once. It had no placebo arm, measured nothing about symptoms, and did not test repeated use; the authors call for dose-response and steady-state studies.
The registry
Besides the three completed studies above, ClinicalTrials.gov lists one active glutathione spray trial:
- NCT05266417 — intranasal insulin and glutathione as add-on therapy in Parkinson's disease, phase 2, sponsored by Gateway Institute for Brain Research, 56 participants, recruiting since February 2022, primary completion estimated September 2027 (record updated July 2026).
The other two registry hits for "intranasal glutathione" are not glutathione sprays: an intranasal insulin trial and an intranasal oxytocin trial that measured oxidative stress.
What is sold, and how
On Drugs@FDA, glutathione appears only as an ingredient — oxidised glutathione — in eye-surgery irrigation solutions such as Alcon's BSS Plus; no glutathione drug is approved to treat anything, nasal or otherwise (read 27 October 2026). Nasal sprays are supplied two ways: by compounding pharmacies on a prescription, often through longevity and wellness clinics, or as over-the-counter supplement sprays. Both are outside FDA's effectiveness review. Glutathione in solution also oxidises over time, so what is in a bottle by the end of its use depends on how it was made and stored — a question for the product's own stability data, which sellers rarely publish. How to read what a seller does publish is on our certificate of analysis guide.
The same seller logic is applied to NAD+, with even less human data: our NAD+ nasal spray page found no published human study at all.
What is not established
- Any benefit over placebo in any condition, including Parkinson's, the only one tested.
- Effects in people without Parkinson's — energy, immunity, skin, detoxification, long COVID, ageing: none tested.
- Long-term safety beyond three months, and whether the one cardiomyopathy case was related.
- Whether a single-dose rise in brain glutathione is sustained with repeated use.
- Product quality of compounded or supplement sprays.
Anyone with Parkinson's considering a supplement alongside treatment should raise it with the neurologist; the published trial record is short enough to read together.
Sources and dates
- Mischley LK et al. A randomized, double-blind phase I/IIa study of intranasal glutathione in Parkinson's disease. Mov Disord. 2015;30(12):1696–701. PMID 26230671.
- Mischley LK et al. Central nervous system uptake of intranasal glutathione in Parkinson's disease. NPJ Parkinsons Dis. 2016;2:16002. PMID 28725693.
- Mischley LK et al. Phase IIb study of intranasal glutathione in Parkinson's disease. J Parkinsons Dis. 2017;7(2):289–99. PMID 28436395.
- PubMed E-utilities searches as printed in the census table — 27 October 2026.
- ClinicalTrials.gov API v2: NCT01398748, NCT02324426, NCT02424708, NCT05266417 and the "intranasal glutathione" query — read 27 October 2026.
- Drugs@FDA via openFDA, active ingredient glutathione: two irrigation-solution applications (glutathione disulfide), no treatment product — 27 October 2026.