Milk Allergy vs. Milk Intolerance: What's The Difference?

Milk allergies are becoming more common, especially in babies and small children. There is some confusion about what is an allergic reaction and what is intolerance, even in the medical world.

Yet there is a distinct difference between the immunological reaction (allergy) and the non-immunologic reaction (intolerance) and the potential dangers of either.

Milk Allergy vs Milk Intolerance

The most common milk people react to is cow's milk. Cow's milk allergy (CMA) is separated from cow's milk intolerance (CMI) by symptoms and reactions. CMA is an immune system response, just as are other food allergies, while CMI is generally a gastrointestinal response. An overview study conducted in 2002 separated the two definitively (see that here).

The fundamental difference is that most CMI reactions are based on lactose (sugars) while most CMA responses are based on proteins. With an intolerance, it can often be avoided by using products that are lactose-free. With an allergy, the person may be allergic to one or all of the proteins in milk, thus requiring that the milk be avoided entirely.

Milk Proteins

People who are allergic to cow's milk will be allergic to either the caseins or whey proteins or both. Caseins are the "curd" portions of the milk (it's solids) and comprise about 80 percent of the milk's protein content. Whey is the liquid portion and accounts for the other 20 percent of the proteins in milk.


As with other allergens, those who are allergic to milk proteins will have an immunological reaction to the proteins entering their system that over-compensates for the "invasion" and releases histamines and other chemicals in response. This triggers several symptoms for the milk allergy sufferer:

Common Milk Allergy Symptoms

Within minutes (sometimes hours) of eating milk, the allergy sufferer will have some or all of the following reactions:

  • Wheezing or coughing
  • Hoarseness
  • Throat tightness
  • Trouble breathing
  • Stomachache or vomiting
  • Itchy, watery, swollen eyes
  • Hives or red spots
  • Swelling

Other symptoms like diarrhea or blood pressure drops could also occur, usually as a longer-term or late reaction and often after some of the above reactions have taken place.

Finally, the most severe reaction is anaphylaxis, usually beginning with the above respiratory reactions which quickly become worse until they become life-threatening.

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