Milk makes up an important part of your diet, and generally it will not cause diarrhea unless you're lactose intolerant. Digestive upset in lactose intolerance develops because the body is missing an enzyme, called lactase, that digests the lactose in milk, instead of leaving it undigested and able to cause problems. If you develop diarrhea after drinking milk, consult your health care professional.
Lactose intolerance is the inability of the small intestine to produce enough lactase to properly digest the milk-sugar. Infants produce sufficient amounts of lactase to digest breast milk. During adulthood the body slows down lactase production. MedlinePlus, an online resource of the Institutes of Health, explains that before there were diary farmers, many people didn’t consume milk so their bodies stopped creating the enzyme after infancy.
Diarrhea is one of the most common symptoms that develops shortly after drinking milk. You may experience abdominal cramps, bloating, gas, foul-smelling stools and floating stools. In severe cases of lactose intolerance you may lose weight, become dehydrated and experience malnutrition.
According to the National Digestive Disease Information Clearinghouse, diarrhea can lead to dehydration, which can lead to further complications. When you’re dehydrated your body has lost too much fluid, which can cause your body to malfunction. Signs of dehydration include dry skin, thirst, fatigue, lightheadedness and dark-colored urine. To prevent dehydration, drink increased liquids, such as water, herbal teas and sports drinks with electrolytes.
If you develop diarrhea after drinking milk along with other symptoms, you may be allergic to milk. A milk allergy is uncommon in adulthood but could develop at any age. Common milk allergy symptoms are hives, eczema, asthma, nasal congestion and other gastrointestinal complications, according to the American Academy of Allergy, Asthma and Immunology. A severe allergic reaction to milk can be life-threatening. Talk with your doctor if you suspect you’re allergic to milk.
Lactose intolerance is incurable, but manageable. Avoiding the consumption of lactose is the best way to prevent lactose intolerant symptoms, according to MedlinePlus. Buy special lactose-free diary products or substitute dairy with rice or soy-based products. You can also purchase lactase enzyme supplements that can be taken at the first bite or sip of milk to prevent symptoms.
The best treatment for diarrhea from lactose intolerance is to drink more water to prevent dehydration. Once you’ve ingested the dairy, you will experience adverse symptoms until the milk passes from the body. The National Digestive Disease Information Clearinghouse recommends avoiding foods that are high in fiber, sweets, caffeinated beverages and foods and greasy foods until the diarrhea has subsided.