Always wash hands after diaper changes or, once your child is potty trained, when done helping him get clean after using the toilet. Teach this lesson to your child as well. If your child is a newborn or young baby, discuss this with your pediatrician first. Diarrhea causes dehydration. Again, check this out with your pediatrician for her specific preferences.
Diarrhea can also cause a nasty bout of diaper rash.
Keep plenty of diaper rash ointment on hand for these occasions. There is little worse than having the runs and a diaper rash all at once. This could cause digestive problems. If your child is on solid foods, make sure there is plenty of fiber in her diet to avoid constipation. If there is blood in or on the stool, inform your pediatrician.