Gastroenteritis describes a group of diseases affecting the stomach or part of the intestine.  Symptoms are often diarrhoea, sickness and stomach ache. Due to the lining of the stomach likely to be inflamed, medicines are often immediately vomited up. 

Large quantities of water, orange juice, or thin soup should be taken to counter the effects of dehydration. Consult your doctor if vomiting persists for more than a day.