Milk Allergy

Allergic to Dairy Foods

Toddler girl holding glass of milk
Henglein and Steets/Cultura/Getty

Milk allergy is the most common food allergy for children, and is the second most common food allergy for adults. The rate of milk allergy, similar to other food allergies, seems to be increasing, and affects at least 3% of all children. While it is relatively common for children to outgrow their milk allergy, sometimes at very young ages, milk allergy can persist into adulthood and even last a lifetime.

What Causes Milk Allergy?

Cow’s milk contains many allergens, which are most commonly broken down into the casein and whey components. The whey components include alpha and beta-lactoglobulins, as well as bovine immunoglobulin. The casein components include alpha and beta-casein components. Allergies to the lactoglobulin components tend to be more easily outgrown by children, whereas allergies to the casein components tend to persist into adolescence or adulthood.

In children and adults who are predisposed to allergic diseases, the body produces allergic antibodies against various milk allergens. These allergic antibodies bind to allergic cells in the body, called mast calls and basophils. When milk or dairy products are consumed, these allergic antibodies bind to the milk proteins, causing the allergic cells to release histamine and other allergic chemicals. These allergic chemicals are responsible for the allergic symptoms that occur.

What are the Symptoms of Milk Allergy?

Symptoms of milk allergy may vary from person to person. Classically, milk allergy most often causes allergic skin symptoms such as urticaria (hives), angioedema (swelling), pruritus (itching), atopic dermatitis (eczema) or other skin rashes. Other symptoms may involve the respiratory tract (asthma symptoms, nasal allergy symptoms), gastrointestinal tract (nausea, vomiting, diarrhea), and even anaphylaxis.

These classic symptoms of milk allergy are caused by the presence of allergic antibody, and are referred to as being “IgE mediated”.

Milk allergy not caused by allergic antibodies, referred to as “non-IgE mediated,” can also occur. These reactions are still caused by the immune system, as opposed to reactions not caused by the immune system, such as with lactose intolerance. These non-IgE mediated forms of milk allergy include the food protein-induced enterocolitis syndrome (FPIES), food protein-induced proctitis, eosinophilic esophagitis (EoE; which can also be IgE-mediated) and Heiner syndrome.

How is Milk Allergy Diagnosed?

IgE-mediated reactions to milk are typically diagnosed with allergy testing, which can be performed using skin testing or by demonstration of IgE against milk protein in the blood. Skin testing is the most accurate way to diagnose milk allergy, although blood testing is helpful in determining when and if a person is likely to have outgrown a milk allergy.

The diagnosis of the non-IgE mediated milk allergy reactions is more difficult to make, and allergy testing is not useful.

Most commonly, the diagnosis is made based on symptoms and the lack of allergic antibodies being present. Sometimes, patch testing can be helpful in the diagnosis of FPIES and EoE, and blood testing for IgG antibodies is used to diagnose Heiner syndrome.

How Is Milk Allergy Treated?

The only widely accepted treatment of milk allergy at the present time is avoidance of milk and dairy products. Oral immunotherapy (OIT) for milk allergy is currently being studied at medical universities around the world, with promising results. OIT involves giving very small amounts of milk protein orally to people with milk allergy, and gradually increasing the amount over time. This often results in a person being able to tolerate fairly large amounts of milk protein over time. It is important to realize, however, that OIT for milk allergy can be extremely dangerous, is only being performed in university settings under close medical supervision. OIT for milk allergy is likely to be many years away from being performed by your local allergist.

Learn how to follow a milk-free diet.

How Often is Milk Allergy Outgrown?

Many children will eventually outgrow their allergy to milk, especially those with non-IgE mediated allergy. For those with an IgE-mediated milk allergy, it may not occur as quickly as previously thought. Older studies suggested that 80% of children outgrow milk allergy by age 5; a more recent study performed on a larger number of children suggests that nearly 80% of children do outgrow milk allergy – but not until their 16th birthday.

Measuring the amount of allergic antibody to milk can help predict the likelihood of a person outgrowing their allergy to milk. If the allergic antibody to milk is below a certain level, an allergist may recommend performing an oral food challenge to milk under medical supervision. This is the only safe way to truly see if a person has outgrown their milk allergy.

Learn more about outgrowing food allergies.


Fiocchi A, Schunemann HJ, Brozek J, et al. Diagnosis and Rationale for Action Against Cow’s Milk Allergy (DRACMA): A Summary Report. J Allergy Clin Immunol. 2010;126:1119-28.

Skripak JM, Matsui EC, Mudd K, Wood RA. The Natural History of IgE-Mediated Cow’s Milk Allergy. 2007; 120:1172-7.

Continue Reading