Food poisoning or allergy is one of the main reasons for diarrhea after eating. It can be due to viral infection on the gastroenteritis region. Many a times, consuming allergic foods without knowledge will end up in diarrhea very often. Irritable bowel syndrome can also cause frequent passage of stools with watery discharge.
Stomach flu which is also called viral gastroenteritis is the major cause for diarrhea after eating. It is not possible to retain anything in the stomach if you develop stomach flu. The symptoms are nausea, vomiting, cramps in stomach, fever, chills and pain in abdomen. The stomach flu is contagious and will last for 3 days.
Diarrhea can be due to food poisoning and allergy to food. It usually occurs when you eat in a new place and you will feel sick within hours of eating. Eating contaminated food or drink can cause continuous diarrhea even for days together. The main reason is due to lack of hygiene and eating uncooked food.