A dog that has suffered from diarrhea for more than a day should be taken to the vet to check for underlying health issues. Otherwise, if a dog has diarrhea, its food should be withheld for 12 to 24 hours. However, it should have plenty of fresh water to drink.
Diarrhea in a dog, while not generally a reason to be concerned, can be caused by a number of factors. A change in diet, ingesting spoiled food or toxic substances, and bacterial or viral infections are some common causes. Kidney and liver diseases are other possible causes, so prolonged cases should be checked by a veterinarian.