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Lactose Intolerance vs. Milk Allergy

Lactose intolerance is not the same as a milk allergy, which involves your immune system.

Lactose is the sugar in milk. If you're lactose intolerant, a glass of milk or a bowl of creamy soup can give you intestinal trouble like cramps, gas, diarrhea, or bloating. That's because your small intestine isn’t making enough of the enzyme lactase. Lactase breaks down milk sugar so your bloodstream can absorb it well.

A milk allergy can cause stomach pain, bloating, and diarrhea, too. But it can also cause hives, swelling, and more severe symptoms, like a drop in blood pressure and trouble breathing.

“If you think you have lactose intolerance, get tested so you have a clear diagnosis,” suggests Beth Kitchin, PhD, RDN. She's an assistant professor of nutrition sciences at the University of Alabama at Birmingham. "The dietary advice for each is really different, so getting an accurate diagnosis is important.”

First, your doctor may suggest you avoid all milk products briefly to see if your symptoms improve. If they do, the doctor may do a test to confirm that you are lactose intolerant.