Are there any side effects to taking glutathione?

Stomach upset: Glutathione is usually well tolerated. Some people may have some stomach upset. Please realize that stomach acid destroys most of the glutathione you take - very little of it will ever make it into your body. Nac (n-acetylcysteine) pushes your natural pathways to make more glutathione. Nac actually does survive stomach acid and can make it into your body. B vitamins, zinc, vit c can also help.

Yes depends on route: There are some studies that show that ingested glutathione is broken down and does not effectively raise your blood levels of glutathione but may lower your zinc levels. Inhaled glutathione may trigger asthma or wheezing attacks. While it has been claimed to provide anti oxidant effects and may be useful in countering side effects of chemotherapy, its effectiveness/risks are poorly understood.