Casein Allergy Overview

Medically Reviewed by Carol DerSarkissian, MD on November 19, 2022
5 min read

If a glass of milk or a slice of pizza causes swollen lips, hives, or other significant symptoms, you may have an allergy to casein, a protein in milk. Another milk protein associated with food allergies is whey. Some people are allergic to both casein and whey.

Most people with an allergy to milk have symptoms which appear when they are infants and outgrow them as they get older. However, some people do not outgrow these symptoms and continue to be allergic as adults. It is unusual to develop an allergy to milk proteins later in life. However, the development of lactose intolerance tends to increase with age. Symptoms include bloating, pain, gas, diarrhea or gastroesophageal reflux. Lactose intolerance is not an allergy but an intolerance, where individuals are unable to digest lactose, the sugar in milk. Lactose intolerance is uncomfortable but not life threatening. It is, on the other hand, important to learn how to recognize and avoid potential allergens.

A casein allergy occurs when your body's immune system mistakenly thinks the protein is harmful and inappropriately produces allergic (IgE) antibodies for protection. Within minutes, the interaction between these antibodies and the specific protein triggers the release of body chemicals such as histamine that cause symptoms which may include:

The most serious reaction to milk allergy is called anaphylaxis. This is a potentially life-threatening reaction that can occur rapidly. Allergy to foods (including casein in milk) is believed to be the leading cause of anaphylaxis outside the hospital setting. People who have asthma and food allergies are at greater risk of complications and death if they develop an anaphylactic reaction.

Symptoms such as swelling inside your mouth, chest pain, hives or difficulty breathing within minutes of consuming a milk product may mean you are experiencing an anaphylactic reaction and need emergency medical attention.


If you are diagnosed with a food, or specifically milk or casein, allergy, your doctor may advise you to carry injectable epinephrine with you in case you accidentally eat a food containing casein and have a reaction. Your doctor or pharmacist can show you how to give the epinephrine. You may also want to keep an over-the-counter antihistamine on hand to help alleviate allergy symptoms. In the case of a severe or serious reaction, though, the antihistamine will not be effective. In that case, you need epinephrine, which is the same as adrenaline, the chemical your body produces at times of excitement or stress.

If you experience a severe allergic reaction with symptoms of anaphylaxis, give yourself the epinephrine to counteract the reaction until help arrives. Do not hesitate to use the epinephrine auto-injector, even if you aren’t sure that you are having an allergic reaction. The medication won’t hurt and could save you. Call 911 for emergency help. Because up to one-third of anaphylactic reactions can have a second wave of symptoms several hours following the initial attack, you may need to be observed in a clinic or hospital for four to eight hours after the initial reaction.


The best treatment for milk/casein allergy is prevention or avoidance. To prevent an allergic reaction to casein, you must follow a casein-free diet, avoiding all foods that contain milk or milk products.

Avoiding milk products involves more than just leaving the cheese off your sandwich. It may also mean leaving off the deli meat if it was cut with the same equipment used to slice the cheese. Even miniscule amounts of casein may be enough to trigger a reaction. In people who are allergic, the level of sensitivity varies from person to person. Some individuals might be able to tolerate small amounts of milk, especially if the milk is baked or cooked in items. However, for most individuals, strict avoidance is best since the amount of milk may not be consistent between products from different manufacturers or even between batches from the same manufacturer.

Giving up milk doesn't have to mean giving up calcium. Because even people who drink milk often don't get enough calcium in their diets, many other foods -- including juices, cereals, almond milk, and rice and soy drinks -- are now enriched with calcium. Vegetables including kale, spinach, and broccoli are good sources of calcium as well.

Whenever you're selecting packaged foods, always check the label for milk ingredients -- even with foods like luncheon meats and candy.

In addition to casein, ingredients and foods to watch for and avoid include:

  • Calcium casein, casein hydrolysate, magnesium casein, potassium casein, rennet casein, sodium casein
  • Dairy products like cheese, yogurt, milk, pudding
  • Butter, butter flavoring, butter fat
  • Lactalbumin, lactoalbumin phosphate, lactaglobulin, lactose
  • Margarine
  • Nondairy creamers
  • Whey, whey hydrolysate

For food products sold in the U.S., manufacturers now must list on the label whether a food contains any of the most common allergens. If a food contains casein, you should find words somewhere on the label such as: "contains milk ingredients," "made with milk ingredients," or "processed in a facility that also processes milk products."

Here are some more tips for casein-free eating:

  • Instead of ice cream, try fruit-flavored soy or rice-based frozen desserts, sorbets, and puddings. There are also ice creams made from coconut milk available.
  • Use vegetable margarine for cooking and to spread on toast.
  • Avoid foods fried in batter, which may contain milk. In some cases, foods fried in oil that has been used to fry something containing milk might be contaminated with small amounts of milk and can cause a reaction.
  • When eating out, ask the wait staff detailed questions about menu items and tell them you are allergic to milk.
  • Explore new foods like vanilla-flavored soy milk, which some people prefer to cow's milk.

It may be a challenge to eliminate all milk from your diet, but with a little effort you can still have proper nutrition with foods you enjoy.