Hello, thanks for posting your query. As your brother is having G6PD deficiency which is an inherited disease causing hemolytic anemia. Vomiting may be due to viremia/ acute viral illness as people with G6PD deficiency are prone to infections. However, there are some drugs and irritants that may trigger heamolysis and present with abdominal pain, nausea, and vomiting. These drugs and substances include primaquine, salicylates, sulfonamides, methylene blue, pollens and fava beans. for more visit (http://www.g6pd.org/en/G6PDDeficiency/SafeUnsafe/DaEvitare_ISS-it) Treatment is supportive and transfusions are needed in crisis. Patients are advised to avoid infections drugs or substances that initiate hemolysis. Consult you doctor for further information. Hope it helps. Take Care!