glutathione manufacturer Best Injections Supplier & FDA highlights concerns with using

Purity: Independently tested (COA available)

It functions as a cofactor for lysyl oxidase (the enzyme responsible for collagen cross-linking and stabilization), ceruloplasmin (a copper transport protein with antioxidant activity), and superoxide dismutase (SOD, a primary antioxidant defense enzyme)

Exogenous addition of GSH has been shown to act as a depigmenting agent, suggesting that other antioxidants may also have the potential to act as depigmenting agents for the treatment of human hyperpigmentation disorders

Siewinski M., et al

Supplement with glutathione: Transdermal supplementation with Glutaryl provides high efficacy

These factors are environmental and dietary, among others