Eating onion diarrhea, may be allergic factors, acute gastroenteritis, indigestion and other reasons. 1. Allergic factors: some people with allergies may be allergic to onions, so after eating an allergic reaction caused by stomach pain, diarrhea. 2. Acute gastroenteritis: onions are left too long to deteriorate, and eating onions that carry bacteria can lead to acute gastroenteritis and diarrhea. 3. indigestion: eating too much onion leads to indigestion, not fully digested food into the intestinal tract, stimulate intestinal peristalsis speed up caused by diarrhea. Eating onions diarrhea is recommended to seek medical advice, identify the cause of the disease and follow the doctor’s instructions.