Tamiflu is fda approved to treat the flu in people 2 weeks and older whose flu symptoms started within the last two days. before taking tamiflu tell your doctor if you're pregnant, nursing have serious health conditions, or take other medicines. if you develop an allergic reaction, a severe rash, or signs of unusual behavior, stop taking tamiflu and call your doctor immediately. children and adolescents in particular may be at an increased risk of seizures, confusion or abnormal behavior. the most common side effects are mild to moderate nausea and vomiting. call your doctor right away. don't ...