Milk allergy or lactose intolerance?

Dear Alice,

This may sound like a dumb question... But I really am unsure. What is the difference between a milk allergy and lactose intolerance? Or are they one in the same? I was in an accident when I was 14. I had emergency surgery on my liver and spleen. After about the age of 20, I have developed severe mad dashes to the restroom after eating anything dairy.

But I have a lot of sinus allergies... that seem to flare up after eating milk products. Although generally milk products do cause thickening of the mucus... I was wondering if severe congestion also goes with it? I no longer eat milk products, of course. But I recently read about a child with a milk allergy who could not breathe through his nose afterward... accompanied by severe coughing. I am now 40 and learned my lesson well... But still curious and always looking for additional info and answers!!


Dear Kathy,

Your question doesn't seem dumb at all! Many people confuse allergies with intolerances or mistakenly use the terms interchangeably. So, with that being said, what exactly is the difference? Intolerance is a physical reaction to a substance that usually doesn't involve the immune system. An allergy, on the other hand, is an immune response, meaning that the body senses that a harmful substance has entered it, causing the body to release specific chemicals to combat the perceived threat. In some cases, an allergy may be life threatening. Due to these different types of reactions, many of the symptoms of each are different (though they both may affect the gastrointestinal systems). 

A food intolerance is a reaction in the body that can cause a reaction that causes discomfort. For example, lactose intolerance occurs when a person has a deficiency in lactase — the enzyme that breaks down lactose, which is the carbohydrate found in cow's milk. So, because this milk sugar isn't digested properly, it can ultimately cause abdominal discomfort, gas, and diarrhea. In order to help tolerate foods containing lactose, individuals can take lactase enzyme supplements and reduce their intake of lactose dairy products. While the experience of consuming it may be unpleasant, reactions to food intolerance are generally limited to the gastrointestinal systems.

A food allergy, on the other hand, can affect more systems in the body. In terms of a milk allergy, your body identifies the proteins in milk and milk products, specifically casein or whey, as harmful. This then causes your immune system to produce immunoglobulin E (IgE) antibodies to attack and destroy these milk proteins. Additionally, the presence of the IgE antibodies also triggers your body to releases chemicals such as histamines to further combat the "foreign substance." This production of antibodies and chemicals can cause allergic symptoms that may affect your gastrointestinal tract, skin, respiratory system, or cardiovascular system. In terms of the effects on a person's respiratory system, this could include having a runny nose, cough, asthma, and anaphylaxis. In the case of foods, studies show that food allergies rarely cause nasal symptoms or wheezing without also causing skin or gastrointestinal symptoms.

Given the symptoms you're experiencing, it seems possible that you may have a milk allergy, though only a health care provider can make that diagnosis. Seeking guidance from a medical professional can help guide you towards appropriate diagnosis and treatment. Other substances found in milk can also trigger allergic reactions in some people, including antibiotics given to cows, or the proteins of ragweed, linseed, peanut, or wheat that make their way into milk. People with a milk allergy may need to cut milk out of their diet entirely.

All in all, diagnosing food allergies is complex, and having symptoms that seem like a milk allergy doesn’t necessarily rule out the possibility of also having an intolerance to lactose. You have found that cutting milk products out of your diet works well for you, which is a great step. It may make sense to see your health care provider to learn more about your own specific situation.

Good luck!

Last updated Jan 14, 2022
Originally published May 02, 2003