Hi welcome to H.C.M.Forum. for some people gastric mucosa
is allergic to some substances like milk, citrus juices, alcohol ect. when such allergy
is there if some one takes that substance they will have such indigestion
like reaction and belchings. if allergy is the case he has to avoid such foods. some times due to sour fruit juices causes gastric irritation and cause belching, in this case, antacids and ppi's can help temporarily. thank you.