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Cow's Milk Protein Intolerance

What is Cow's milk protein intolerance?

Cow’s milk protein intolerance (CMPI) is an abnormal response by the body's immune system to a protein found in cow's milk, which causes injury to the stomach and intestines. Cow's milk protein intolerance is not lactose intolerance.

Risk factors for having CMPI includes having a relative (particularly a first degree relative like a sibling or parent) who has a history of CMPI, or has atopic disease or allergic disease. Breastfeeding may protect infants from developing CMPI, but sometimes those proteins can be found in breastmilk if mom has ingested cow's milk herself.

CMPI can be IgE-mediated or non-IgE mediated. Immunoglobulin E is an antibody typically seen in allergic disease. In IgE-mediated CMPI, symptoms can start within 2 hours of drinking cow milk, whereas in non-IgE-mediated CMPI, symptoms can happen from 2 days to 1 week after ingestion of cow's milk.

Signs and Symptoms

CMPI symptoms will usually develop within the first week of starting cow’s milk in their diet. The signs might manifest as a skin rash or eczema, or involve the GI tract, such as vomiting, abdominal pain, blood in the stool, mucousy stool, and diarrhea. Prolonged issues in infants could lead to wheezing, irritability and poor growth / failure to thrive.


History and physical examination are the most helpful investigations in diagnosing CMPI. Timing of the symptoms, age of the patient, and symptoms related to feeds are key to diagnosis. There may be microscopic blood in the stool due to damage to the intestines. The diagnosis of CMPI is also supported by an improvement in symptoms after the elimination of cow's milk. Most of the time, blood tests and other invasive studies are not helpful.


The main treatment of CMPI is to remove cow's milk protein from the diet Typically, the diet starts with an extensively hydrolyzed formula which is a formula of broken down proteins Soy milk / goat's milk / sheep's milk are not appropriate alternatives in most children. A small percentage of patients may require an elemental (amino acid based) formula.

It is possible to continue breastfeeding infants with CMPI. In order to do so, the mother will need to eliminate all dairy and soy products from the diet. Since, it can difficult to know which foods contain dairy or soy, we will usually have mother’s meet with a nutritionist if they have any questions.

Most infants that are started on cow’s milk-free formulas or breastfed by a mother on a milk-free/soy-free diet will need to remain on the diet until about 12 months of age. At that point, the child can be challenged with cow’s milk. Most kids will outgrow CMPI by one year of age. However, if they do not, the majority will do so by 3 years of age.


University of Rochester Medical Center, Department of Pediatrics, Gastroenterology, Hepatology and Nutrition Division