Casein allergy, or milk protein allergy, is an immune reaction to a protein found in cow's milk, most commonly the alpha S-1 casein protein. The condition is common in children, with symptoms that develop quickly or gradually, including swollen lips, skin rash, runny nose, and coughing.

A casein allergy can be easily confused with lactose intolerance because they share many of the same symptoms, and lactose, a sugar, is also in most milk products. However, casein allergy is an immune response, whereas lactose intolerance is caused by the person's inability to metabolize lactose. Some people outgrow their casein allergies, while others need to modify their diets.

Casein Allergy is Common in Young Children

Casein allergy is fairly common, with over 200,000 cases reported in the U.S. every year. Between 2% and 4% of children in their first year experience casein allergies or sensitivity, with cow's milk being the primary cause of food-related allergies in young children.

A casein allergy typically develops at around 3 months, but goes away or is substantially reduced by their 5th birthday.

Little boy with dairy allergy holding glass of milk indoors. Child with painful expression after drinking milk. Lactose intolerance. ozgurcankaya / Getty Images


Symptoms Can Be Severe

Common symptoms of casein allergy include swollen lips and tongue, skin rashes, and abdominal cramping. These are all caused by the release of histamines as part of the body's immune response to casein.

In rare cases, the symptoms can be more severe and even lead to anaphylaxis, which can be life-threatening. Parents of children with severe casein allergies should always carry EpiPens in case of emergency.

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Breastfeeding Can Cause Symptoms

Breastfeeding mothers can transmit casein from cow's milk to nursing babies. For this reason, even babies that have never been formula-fed can develop food allergies from breast milk.

While it can be a challenge to narrow down the cause of a food allergy in a breastfeeding infant, eliminating dairy products from a mother's diet is a good first guess.

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Genetics and Other Factors Contribute

While science is still working to understand casein allergy, it has determined several factors that can cause it in infants. Casein allergy can be passed down genetically by a child's parents, and exposure to casein early on can give rise to certain symptoms.

Aside from genetics and exposure, certain environmental factors play a part. Exposure to pets, second-hand smoke, and other allergens may contribute to developing a casein allergy.

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Casein Sensitivity is Not the Same as Casein Allergy

Casein sensitivity, sometimes referred to as casein intolerance, is a less severe form of a casein allergy. While casein allergy symptoms tend to be more dramatic and immediate, symptoms from casein sensitivity can appear up to 72 hours after ingesting milk products and include bloating or an upset stomach.

Casein sensitivity is easy to confuse with lactose intolerance. A food sensitivity test can help determine the root cause of food-related symptoms.

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Casein Allergy is More Common Among Certain Populations

East Asian, non-black Hispanic, and Native American populations show a higher rate of allergies and intolerance to milk products than European or Central Asian populations. Relative to the prevalence of casein allergy, however, the same groups are much more susceptible to lactose intolerance from milk products.

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Even Small Amounts of Casein Can Cause a Reaction

Especially for those with an extreme allergy to casein, even exposure to small amounts of the protein can cause potentially life-threatening symptoms. People with a severe casein allergy not only have to avoid consuming foods that contain milk products of any kind but also avoid purchasing food from places where cross-contamination could be possible—for instance, buying meat from a deli where the same knife may have been used to slice cheese.

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There is No Cure for Casein Allergy

There is no cure for casein allergy, however, it can be treated to the point where it is in remission.

The Food Allergy Institute's Tolerance Induction Program (TIP) aims to help young children with food allergies move toward food freedom through a specialized exposure treatment program. TIP uses exposure to proteins similar to casein to train a patient's immune system to gradually tolerate milk products.

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A Dairy-Free Diet Can Help Prevent Symptoms

As dairy allergies are fairly common, there are a variety of substitute food items on the market that are casein-free. Almond milk, soy milk, and rice milk offer a similar mouthfeel to cow's milk, without the presence of casein, bovine hormones, or antibiotics.

Products like potato chips and snacks often contain milk products in small amounts. While displaying the ingredients is mandatory, extreme caution is advised for those at risk of anaphylaxis.

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Antihistamines are an Effective Treatment

Casein allergy produces a histamine reaction in the form of swelling, hives, and trouble breathing. An over-the-counter antihistamine can combat symptoms of this immune response, though these medications can cause drowsiness and other side effects.

For parents of small children with casein allergies, carrying an EpiPen on hand at all times can be a life-saving strategy in case of a more severe reaction.

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