Lactose intolerance is sometimes confused with milk allergy, but the two are quite different. Milk allergy is an immune reaction to a protein in milk, usually casein. Lactose intolerance is not an immune condition. People with lactose intolerance don’t have an immune reaction to lactose; they simply have low or no production of the enzyme which breaks it down, and experience digestive symptoms resulting from the fermentation of lactose by their intestinal bacteria.[1]
What’s the difference between milk allergy and lactose intolerance?
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•Last Updated: May 16, 2025
Lactose intolerance differs from milk allergy in that it is not an immune reaction; instead, it results from low or no production of the enzyme needed to break down lactose, which leads to digestive symptoms. In contrast, milk allergy involves an immune response to milk proteins, typically casein.