In ancient times, it was recorded that onion and honey could not be taken together. Now, there are reports about acute gastroenteritis symptoms such as nausea, vomiting, abdominal pain and diarrhea after honey and onion were eaten together. So honey can't be eaten with onions. Onion contains more crude fiber, which can promote gastrointestinal peristalsis, and honey also moistens intestines. These two kinds of food are easy to have diarrhea when eaten together.