No treatment is without complications, and stem cell therapy is the same. However, despite its novelty, stem cell therapy has limited side effects, if used properly, with comparable general side effects to those experienced with regular blood transfusion or foreign organ transplantation (ex. allergic reactions, cell rejection, or fever). Other side effects that have been specifically reported in clinical trials testing stem cell therapy in autism include:

• Headaches
• Pain at site of injection
• Gastrointestinal disturbances including nausea and/or vomiting
• Seizures
• Initial increase in the degree of hyperactivity for the first three months following stem cell therapy

However, none of these side effects reported were life-threatening or had life-long consequences, and they were easily managed medically at the time of their occurrence.