Casein Allergy Symptoms, Cause, Treatment & Food to Avoid

Casein is a protein found in milk and milk products. It is the most frequently recognized allergen, which is abundant in cow’s milk. In individuals with casein allergy, the immune system identifies casein as a threat or a harmful substance and then triggers a reaction to fight it off. This causes the release of a chemical called ‘histamine’ that leads to adverse allergic reactions in the body. Casein allergy is completely different from lactose intolerance. Lactose intolerance is a condition in which, the body is unable to produce lactose-digesting enzyme ‘lactase’. Hence, one should not get confused between an allergy caused due to milk proteins and an intolerance to milk.

Causes of Casein Allergy

An abnormal response by the body’s immune system against milk and milk products gives rise to allergic symptoms. The body’s immune system gets confused and considers casein to be an allergen. This triggers an allergic response and it is more common among infants and young children. It further causes imbalances between Th1 and Th2 cells, which has a negative impact on the health.

Some studies have found that early contact of infants with cow’s milk protein such as ‘casein’ may lead to hypersensitivity. Therefore, 6 months of exclusive breastfeeding is advised to lactating mothers. However, more studies and research are required to confirm the effect of casein on human health.

Casein protein accounts for 80% of the total milk proteins. This casein fraction consists of 4 different proteins, which include:

  • αS1-casein
  • αS2-casein
  • β-casein
  • κ-casein

Out of the above mentioned 4 protein fractions, αS1-casein is the most important allergen of casein allergy.

Symptoms of Casein Allergy

Symptoms may appear within 1 to 2 hours after ingestion of milk and milk products and it affects the skin, the respiratory system, the gastrointestinal system and may appear as systemic anaphylactic reactions in severe cases.

Skin Reactions:

The immunoglobulin E-mediated reactions affecting the skin may cause:

  • Rashes
  • Redness
  • Flushing
  • Pruritis, itching of the skin
  • Angioedema, swelling of the skin
  • Urticaria or hives

Respiratory Symptoms:

Respiratory symptoms that occur after the intake of casein include:

  • Wheezing
  • Coughing
  • Rhinoconjunctivitis
  • Laryngeal edema
  • Worsening of the asthma

Gastrointestinal Symptoms:

Casein allergy affects the gastrointestinal tract too. Symptoms include:

  • Abdominal pain or stomach ache
  • Nausea
  • Oral itching
  • Vomiting
  • Diarrhea or loose stools


Anaphylaxis is a life-threatening condition and cow’s milk is the third most common food component after tree nuts and peanuts that causes anaphylactic reactions. Symptoms include:

  • Rapid pulse
  • Loss of consciousness
  • Low blood pressure
  • Shortness of breath

Diagnosis and Tests of Casein Allergy

Clinical History:

A specific medical history helps in the diagnosis of the allergy. Tell your doctor about your intake of milk and milk products. Explain him the symptoms, which you observed and tell him after how long did the symptoms appear when you consumed milk or milk products. Do let your doctor know if you have experienced this for the first time or it has happened before. Tell your doctor about your family’s history of food allergies, if any. In case of infants, inform the doctor if cow’s milk was introduced early in the infant’s diet.

After a thorough clinical history, diagnostic tests take place, which help in confirming or ruling out casein allergy.

Oral Food Challenge Test:

Oral food challenge test is performed to obtain a clear diagnosis. During this test, your allergist will feed you casein containing food, for example- milk, in measured doses. The allergist will start with a very small dose and look for signs of reactions or allergy symptoms. If signs and symptoms are present, the test is stopped and allergy is confirmed. If symptoms do not exist, the amount of food is increased. If there are no symptoms till the end of the procedure, your allergist will rule out casein allergy.

Skin Prick Test:

In this test, your allergist pricks or scratches the skin with the help of a lancet. Cow’s milk extract or fresh milk or allergen is placed at the site of the prick. If immunoglobulin E antibodies are present in the body against casein, redness or a bump on the skin may appear. Presence of redness or bump confirms casein allergy.

Atopy Patch Test:

This test can be performed in individuals with atopic dermatitis, gastrointestinal symptoms and individuals with delayed reactions after consumption of casein containing products. During this test, allergens are applied at the back of an individual for up to 48 hours in a sealed patch. The skin reactions are documented after removal of the patches, after another 24 to 48 hours. At the second appointment, which takes place 2 days later, the patches will be removed. The back is marked with a suitable marker to identify the test sites. The back is checked during the third appointment, which takes place after 2 days. Presence of rash, burn-like reactions, red plaques or ulcers indicates a positive allergy test.

Blood Test:

The presence of high amount of immunoglobulin E in the blood indicates that you have an allergy. (1)

Risk Factors

  • Individuals with family history of casein allergy
  • Early introduction of cow’s milk to an infant’s diet

Treatment of Casein Allergy


Anti-histamines are drugs that block the action of a chemical called ‘histamine’, which is responsible for allergic symptoms. These drugs help in relieving allergic symptoms such as, sneezing, nose running and allergic rhinitis.

Epinephrine Shot:

Epinephrine shot is useful when symptoms become severe or during anaphylaxis. It is used to treat life-threatening allergic reactions.


  • Avoid milk and milk containing products, such as cheese, paneer, curd and buttermilk
  • Read the food labels carefully before purchasing any product. Do not purchase foods containing even traces of milk
  • Some food products contain milk in the hidden form, for example breads. Such food products should also be avoided
  • Before ordering any dish at the restaurant, ask the staff about the ingredients used. Tell them about your allergy so that they can be extra careful and this will also help them in suggesting you food preparations that do not contain casein
  • Replace cow’s milk with casein-free milk options, such as soy milk, coconut milk, rice milk and almond milk
  • Replace butter and pure ghee with unrefined cooking oil

List of Foods to Avoid

Below mentioned is a list of foods that contain casein:

  • Cow’s milk
  • Yoghurt
  • Buttermilk
  • Cream
  • Cheese
  • Chocolates
  • Cakes
  • Breads
  • Biscuits and cookies
  • Pudding
  • Custard
  • Ice-cream
  • Cream based soups
  • Butter
  • Pure ghee
  • Protein powders

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Sneha Sadhwani

Dt. Sneha Sadhwani Sewlani (B.Sc. Food Science & Nutrition, PG in Clinical Nutrition & Dietetics) is Clinical Nutritionist & Certified Diabetes Educator and Certified Lifestyle Coach. She has expertise in clinical nutrition and 4 years’ experience working as Clinical Nutritionist and Dietician. She has been associated as a nutritionist with LTMG Hospital and S. L. Raheja Fortis Institute in Mumbai.She has also her own private practice where she offers a wide range of different programs, including weight loss, weight gain, diabetes management, diet plan according to diseases and much more through her in-person and online consultation.Sneha strongly believes that a healthy diet and lifestyle modifications are the best ways to prevent and treat diseases. She says, “Eating healthy is an art, be an artist of your own mind and body”.

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