How to Tell If Allergic to Casein or Milk Protein

Casein is a milk protein present in cow's milk products and can be problematic if you have casein-milk protein allergy. This condition is often confused with lactose intolerance because they share some symptoms and both are triggered by dairy consumption. However, aside from gastrointestinal discomfort, casein allergy can be life-threatening in severe cases, so it is important to differentiate whether you have true casein allergy or lactose intolerance.

A boy drinking milk out of a straw on the table. (Image: noblige/iStock/Getty Images)

Step 1

Know your symptoms. In the case of lactose intolerance, only the digestive system is affected, causing diarrhea, bloating and gas. On the other hand, casein-milk protein allergy usually affects more than just the digestive system, and symptoms resemble those of other food allergies, such as nausea, vomiting, stomach cramps, diarrhea, eczema, hives, wheezing, coughing, congestion, runny nose and in severe cases, anaphylactic shock.

Step 2

Order a skin test with your health care provider. During a skin test, a small amount of casein protein is put into your skin. Watch for any reactions such as swelling or redness of the site during the next 15 to 20 minutes.

Step 3

Eliminate all milk products from your diet, then slowly re-introduce them one at a time and watch for allergic reactions. Foods that contain milk or are derived from milk include baked goods, butter, buttermilk, cheese, chocolate, cream, cream soup, custard, deli meats, ice cream, margarine, milk, pizza, pudding, salad dressing, sherbet, sour cream and yogurt. Other foods may contain milk in their ingredients as well. Always check the food label for ingredients.

Step 4

Order an allergy blood test with your health care provider. This test is also called an allergen-specific IgE antibody test and is used to screen for an allergy to a specific substance or substances--in this case, casein-milk protein.


The accuracy of allergy testing varies and is not 100 percent reliable. For example, a negative result from a blood test means a small chance still exists that you are allergic.


Some medicines may affect the accuracy of a skin test. For example, you should avoid antihistamines before the test as they may lead to a false-negative result. Consult your doctor before the test. Skin and blood tests can lead to certain risks such as allergic reactions and life-threatening anaphylactic shock.

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