If you have diarrhea, you may feel that you can't trust your own bowels. Stools come out watery and too frequently. You may even feel dehydrated and fatigued from the loss of fluids and minerals. Different foods and drinks appear to trigger diarrhea in different people. For example, you may have an increased sensitivity to milk when you have diarrhea because of the lactose it contains.
When you have diarrhea, you may find it difficult to properly digest lactose-rich foods such as milk, according to the National Digestive Disease Information Clearinghouse. Even if you're not normally lactose intolerant, diarrhea that's caused by a virus can make you sensitive to milk products -- sometimes for up to 6 weeks after the diarrhea has cleared. Because you need to produce more of the enzyme lactase to digest lactose, this can cause more watery stools or an irritated bowel.
Diarrhea can have a serious effect on children, so it's important to feed them the right foods during a bout of persistent diarrhea. In a 1996 study published in the journal "Pediatrics," researchers measured whether a dry cereal diet or a milky cereal diet worked best for children with diarrhea. They found that the symptoms of diarrhea generally lasted a similar amount of time. That means that moderate amounts of milk may have no negative effects in children with diarrhea.
In some cases, milk may actually be the source of the diarrhea. Bacteria may grow in unpasteurized milk. For example, a common cause of diarrhea symptoms in America is the bacteria Campylobacter jejuni, which triggers campylobacteriosis, according to Colorado State University Extension. Certainly you should avoid any unpasteurized milk when you have diarrhea to avoid further possible contamination, particularly if you're pregnant.
You may find that yogurt triggers fewer symptoms during a bout of diarrhea than milk does. Yogurt contains less lactose. The University of Maryland Medical Center suggests taking lactase enzyme tablets before drinking milk or dairy. If you know that you're lactose intolerant even when you don't have diarrhea, then you should take extra care to avoid all milk and milk products, which will likely make your diarrhea symptoms much worse.