Milk Protein Allergy

Milk protein allergy occurs in young children, usually in the first few months of life with the introduction of cow’s milk formula to the diet. However, it can also occur in exclusively breastfed infants through the mother’s diet. The most common allergens are casein and whey, two dairy proteins found in cow’s milk.

There are two types of milk protein allergy, IgE-mediated and non-IgE reactions. IgE is a type of antibody made by the immune system to fight allergens. IgE-mediated reactions occur immediately (minutes to 2 hours) after ingestion and include flushing, hives, sudden profuse vomiting, and drowsiness. This requires immediate medical attention with your pediatrician or the ER. Non-IgE reactions have a delayed onset. Symptoms include vomiting, excessive spit-up, persistent facial rash, mucus or blood in stool, or loose stools in well-appearing infants.

What can be done?

For exclusively bread-fed infants, we typically assess the maternal diet for cow’s milk, soy, and other dairy products. Avoidance of dairy may be recommended for mom. For formula-fed babies, there are extensively hydrolyzed formulas available, meaning the milk proteins are broken down prior to ingestion. If you think your child may have milk protein allergy, discuss with your pediatrician what your options are.

Will my child grow out of this?

Many children with milk protein allergy as infants grow out of it by the time they are toddlers. Milk protein allergy is uncommon in adults.

Should I use a soy-based formula?

Switching to a soy-based formula is typically not recommended. Many patients with sensitivity to cow milk also have sensitivity to soy.

Is this the same as lactose intolerance?

No, lactose intolerance is not an immune-mediated reaction but rather due to an absence or deficiency of lactase, which is the enzyme that breaks down lactose. It is rare in infants and usually develops in childhood.