Four glasses of milk
Rachel Dyckman
Rachel DyckmanRegistered Dietitian

Milk Allergy vs Milk Intolerance

Published on August 3, 2021

Food allergies affect a staggering 32 million Americans, and milk is one of the most prevalent allergies in both children and adults. While it is common for children to outgrow a milk allergy over time, this is not always the case.

Other individuals may not be allergic to milk but are intolerant to milk protein or milk sugar. These individuals still experience unpleasant symptoms after consuming milk products, but how can you tell if the symptoms you are experiencing are due to an allergy or an intolerance? What exactly is the difference between the two?

Milk Allergy: What is it, what are the symptoms, and how do you diagnose it?

What is a Milk Allergy?

A milk allergy is an immune reaction to milk protein. The most common type of milk allergy is immunoglobulin E (IgE)-mediated. This means that your immune system views milk protein as harmful and produces IgE antibodies to combat it. Each time you consume milk or milk products, these IgE antibodies recognize the milk protein allergen and activate your immune system. This causes the release of histamine and other compounds that lead to both unpleasant and dangerous symptoms. The two main proteins in milk are whey and casein. The liquid portion of milk contains whey protein, whereas milk curds (the solid portion that curdles) contain casein protein. 

Many people who have a cow’s milk allergy are also allergic to milk from other mammals such as goat’s milk and sheep’s milk. Depending on the severity of a milk allergy, even tiny amounts of milk products can trigger an allergic reaction. This is why it is very important to minimize cross-contamination as much as possible if you have a milk allergy. This means avoiding cookware, utensils, and other equipment that may have been used to prepare milk-containing foods unless they are thoroughly washed. You should also avoid foods that may have come into contact with milk products.


Milk Allergy Symptoms

Symptoms of an allergic reaction to milk can vary. Some symptoms will occur right after a person ingests milk products, while other symptoms may take a few hours to develop. 

Early symptoms of an allergic reaction to milk include but are not limited to:

  • Wheezing
  • Coughing or shortness of breath
  • Swelling of the tongue or mouth
  • Tightening of the throat
  • Vomiting
  • Itching or tingling around the mouth
  • Hives


Later symptoms of an allergic reaction to milk that may take a few hours to develop include but are not limited to:

  • Diarrhea
  • Abdominal cramping
  • Watery eyes
  • Runny nose



In the case of a severe milk allergy, anaphylaxis can occur if milk or milk products are accidentally ingested. Anaphylaxis is a severe allergic reaction that is life threatening. It can cause narrowing of the airways that restricts breathing.


Signs of anaphylaxis include:

  • Swelling or tightening of the throat
  • Difficulty breathing
  • Sudden drop in blood pressure
  • Itching
  • Flushing of the face

Anaphylaxis requires immediate medical attention. Those who are at risk of developing anaphylaxis should carry around an EpiPen shot, which is used to stop or slow down a severe allergic reaction. If you experience a severe allergic reaction and need to use your EpiPen, you should always call 911 or have someone take you to the nearest emergency room right away. This is because it is possible to have a second bout of severe symptoms that requires medical attention.


Milk Allergy Diagnosis 

If you suspect that you may have a milk allergy, it is important that you seek care from your doctor or allergist. They will ask you questions about your symptoms and may perform one or a combination of the following tests to determine if you have an IgE-mediated milk allergy:


Skin Prick Test

For this test, a portion of the skin (usually on the forearm or back) is pricked and exposed to liquid that contains milk allergens. If a raised bump develops at the site of the prick, it is likely that you have a milk allergy. 


IgE Antibody Blood Test

A blood test can also be performed to measure the levels of milk allergen-specific IgE antibodies in your blood. 

It is important to note that it is possible to have “false positive” results from either test. Your doctor or allergist will interpret your results and determine whether or not it is appropriate to have you take part in an “oral food challenge.” 


Oral Food Challenge

For an oral food challenge, you are fed different quantities of milk in a medical setting and observed for allergic reactions. If you develop allergic symptoms, the challenge will stop.


Food Protein Induced Enterocolitis Syndrome (FPIES)

FPIES is a rare form of food allergy that is non-IgE mediated and commonly triggered by milk protein. With FPIES, symptoms are related to the gastrointestinal tract and include severe vomiting and diarrhea. Onset of symptoms usually occurs 2-4 hours after milk consumption. Luckily, this condition is most common in infants and is often outgrown over time.

Diagnosing milk allergy-related FPIES is a bit more complicated. This type of allergy is non-IgE mediated and therefore standard skin and blood allergy tests will come back negative for a milk allergy. It is best to consult your physician or allergist who will assess your health history and symptoms. If appropriate, they may perform an oral food challenge to diagnose FPIES.

Milk Intolerance: What is it, what are the symptoms, and how do you diagnose it?

What is a Milk Intolerance?

A milk intolerance is a non-immune reaction to milk due to an inability to properly digest a component of milk. 

Lactose intolerance 

The most common form of milk intolerance is lactose intolerance or an inability to digest lactose (milk sugar). This occurs when an individual does not produce enough lactase, the enzyme responsible for breaking down lactose in our small intestines. Those with lactose intolerance may choose to take lactase pills when they consume milk products to help break down the lactose so that they can still enjoy these foods. 

Milk protein intolerance 

It is also possible to have a milk protein intolerance meaning your body has difficulty digesting whey or casein proteins. Individuals with milk intolerances may be able to tolerate milk or milk products in small quantities without experiencing symptoms and do not have to be as concerned about cross-contamination compared to those with milk allergies. 


Milk Intolerance Symptoms

Those with a milk intolerance (whether it is lactose or milk protein) experience unpleasant but non-life threatening symptoms after consuming milk or milk products. These symptoms are generally related to the gastrointestinal tract and may include (but are not limited to): 

  • Abdominal cramping
  • Diarrhea
  • Bloating
  • Flatulence
  • Nausea

Onset of these symptoms generally occurs between 30 minutes and 2 hours after milk is consumed and may last between 12 and 48 hours depending on the individual and quantity of milk consumed.


Milk Intolerance Diagnosis 

Lactose Intolerance Diagnosis

The most effective and accurate way to test for most food intolerances is trying a temporary elimination of the suspected offender for 2-4 weeks to see if your symptoms improve. However, there are two other ways to test for lactose intolerance.

Lactose Tolerance Blood Sugar Test

One way is through a lactose tolerance test. For this test, an individual drinks a lactose-containing solution and then has their blood sugar levels checked. If the individual is lactose intolerant, their blood sugar levels may either rise very slowly, or stay the same. This occurs because they are not able to break down lactose sugar into glucose. 

Hydrogen Breath Test for Lactose Intolerance

Lactose intolerance can also be diagnosed with a hydrogen breath test. For this test, an individual fasts overnight and then blows into a device that measures the hydrogen content of their breath. They are then given a lactose-containing solution to drink and have their breath re-tested for hydrogen gas in 15-minute increments over a 2-hour period. If an individual produces a large amount of hydrogen gas, this suggests that lactose sugar was not adequately broken down and made its way into the large intestine. Here, bacteria start to ferment the lactose sugar and produce hydrogen gas as a byproduct, indicating lactose intolerance.

Milk Protein Intolerance Diagnosis

There are a number of food intolerance tests available that claim to assess for milk protein intolerances, but, unfortunately, evidence to support the efficacy of these tests is lacking. 

If you are not lactose intolerant or allergic to milk but still experience symptoms after consuming milk and milk products, then the best way to assess for a milk protein intolerance is to temporarily eliminate milk and milk products from your diet for 2-4 weeks to see if your symptoms improve. Then, try gradually reintroducing milk products back into your diet to see if your symptoms return. If they do, it is likely that you have a milk protein intolerance. 

It is best to work with a Registered Dietitian through this process to help guide you and interpret your symptoms. Keeping a food and symptom journal can also help you or a Registered Dietitian to pinpoint what may be causing your symptoms, as it is possible for other dietary factors to be at play.   

If you have a milk allergy or intolerance, the Fig app can help you identify dairy-free foods at your favorite grocery store. Be sure to read Fig’s Introduction to the Dairy-Free Diet blog post to help you get started.

See a list of all grocery products and whether they are likely milk free.

Image by The Humble Co on Unsplash