Glutathione is an antioxidant that helps in preventing damage of cells from oxidative stress, incidentally it has also been shown to reduce melanin synthesis and has been used as a skin lightening agent.Injectable route by intravenous infusion is more efficacious than oral intake as it is not fully absorbed from the gut. Any injection given into the blood can rarely produce an allergic response from the body's immune system.This can occur with any injection not specific to glutathione.There are no blood tests to predict these allergic reactions.Skin testing with the injection with a Microamount of the infusion  injected under the skin ,if positive ,then there is risk of allergic response during infusion.These allergic reactions if at all occur  can be treated by an experienced doctor with proper set up and facility for resuscitation.So you should always take these injection under the supervision of qualified dermatologist in a proper hospital or clinic set up.