DIARRHEA OVERVIEW. Diarrhea is defined as three or more loose or watery stools per day. Nearly everyone will have an episode of diarrhea at some point during their life, with the average adult experiencing it four times per year. Food and cooking smells, perfume, smoke, stuffy rooms, heat, humidity, flickering lights, and driving are among the possible triggers of nausea and vomiting. Eat bland foods. . Vomiting and diarrhea (gastroenteritis) in dogs and cats can be caused by a virus, parasite, food or health problems. Find out the best treatment for your pet.