It is important that H202 be taken on an empty stomach. This is best accomplished by taking it either one hour before meals or three hours after meals. If there is food in the stomach, the reaction of H202 on any bacteria present may cause excess foaming, indigestion, and possibly even vomiting. Additionally, some animal research indicates that when H202 given orally combines with iron and small amounts of vitamin C in the stomach, hydroxyl radicals are created (J Inorg Biochem 89;35(1):55-69).