Casein Allergy


Allergy Types: Food Allergies: Casein Allergy


What is casein?

Casein is in a family of phosphoproteins that make up 80% of the proteins in cow’s milk. In fact, casein is found in all mammalian milk in varying quantities, including human milk, where it constitutes 25-45% of proteins. It is a complete protein that supplies all the essential amino acids (those that can’t be synthesised naturally by the body).


The name ‘casein’ comes from the Latin word for cheese (‘caseus’) and, indeed, casein is a major ingredient in the production of this food. In cheese-making, the casein in milk from cows, goats or buffalo is typically coagulated into a protease using rennet. Prior to coagulation casein is often called ‘casiogen’ in the UK, whereas the term ‘casein’ is often reserved for the coagulated protein.

Casein is also commonly used as a food additive. It was historically used in artists’ paint and types of glue and plastics and still has a variety of diverse uses due to its binding properties and porosity, such  as a binding for safety matches, an adhesive for labelling bottles and as  an agent in the reminerlaization of tooth enamel in dentistry.

How do I know if I’m allergic to casein?

Lots of people are allergic to either, or both, the casein or whey proteins in milk, though young people are the most susceptible and most people outgrow it. A milk (casein or whey) allergy is different to lactose intoleranceas the proteins trigger an immunogloben antibody response. Even a very small amount of casein can trigger an allergic response. What is the difference between a dairy (milk) allergy and lactose intolerance?


It is easy to diagnose in infants as generally symptoms will develop immediately after they start consuming milk formula, or after a child consumes food containing milk. In adults it can be more difficult to diagnose as we typically consume other foods simultaneously. A doctor may perform skin tests to detect the specific immunogloben antibodies that are responsible for triggering an immediate reaction, like skin rash, as well as look at your clinical history and suggest tests and challenges that isolate the suspect foods. Researchers claim that 1-7% of infants display an allergy to milk, and as many as 60% of those will overcome the allergy by the time they are four years old, 80% by the time they are six. Only 0.1-0.5% of adults have been found to have an allergy to milk.


Occasionally people with a milk allergy can consume pasteurised milk as the pasteurisation process breaks up the whey proteins (and they may only be allergic to whey, rather than casein proteins). Conversely, casein proteins are not broken down by heat so people who are allergic to it are likely to react to all milk products, however they are treated. Not all caseins behave in the same way after you consume them, and sometimes people who are allergic to the casein in cow’s milk can consume goat’s milk, for example, without having an adverse reaction because of the differences in the structure of the casein proteins.

Typical immediate symptoms of an allergy to casein include swelling of the face, mouth, tongue or throat, nasal congestion leading to a runny nose, sneezing, coughing and wheezing, itchy eyes, as well as red, itchy skin, rashes or hives. Other symptoms may take weeks to develop and include a general increase in mucous production, abdominal cramps, loose or bloody stools, and diarrhoea. The allergy can be severe enough to trigger anaphylaxis and so the best treatment is complete avoidance.

Most medical practitioners recommend replacing mammalian milk with soy milk if you are allergic to casein. It is important to ensure that you are still consuming all the essential amino acids that casein provides, but they are readily available in other foods too, such eggs for calcium and amino acids, or nuts and seeds (like brazil nuts and sesame seeds) for phosphorous. 


All true food allergies are caused by an immune system malfunction. Your immune system identifies certain milk proteins as harmful, triggering the production of immunoglobulin E (IgE) antibodies to neutralize the protein (allergen). The next time you come in contact with these proteins, IgE antibodies recognize them and signal your immune system to release histamine and other chemicals, causing a range of allergic signs and symptoms.

There are two main proteins in cow’s milk that can cause an allergic reaction:

  • Casein, found in the solid part (curd) of milk that curdles
  • Whey, found in the liquid part of milk that remains after milk curdles

You or your child may be allergic to only one milk protein or both. These proteins may be hard to avoid because they’re also in some processed foods. And, most people who react to cow’s milk will react to sheep’s, goat’s and buffalo’s milk. Less commonly, people allergic to cow’s milk are also allergic to soy milk.

Food protein-induced enterocolitis syndrome (FPIES)

A food allergen can also cause what’s sometimes called a delayed food allergy. Although any food can be a trigger, milk is one of the most common. The reaction, commonly vomiting and diarrhea, usually occurs within hours after eating the trigger rather than minutes.

Unlike some food allergies, FPIES usually resolves over time. As with typical milk allergies, preventing an FPIES reaction involves avoiding milk and milk products.

 Risk Factors

Certain factors may increase the risk of developing a casein allergy:

  • Other allergies. Many children allergic to milk also have other allergies. Milk allergy is often the first to develop.
  • Atopic dermatitis. Children who have atopic dermatitis — a common, chronic inflammation of the skin — are much more likely to develop a food allergy.
  • Family history. A person’s risk of a food allergy increases if one or both parents have a food allergy or another type of allergy — such as hay fever, asthma, hives or eczema.
  • Age. Milk allergy is more common in children. As they age, their digestive system matures, and their bodies are less likely to react to milk. 


When food causes an allergic reaction, it isn’t always easy to pinpoint what food is to blame. To evaluate whether you or your child has a milk allergy, your doctor may:

  • Ask detailed questions about signs and symptoms
  • Perform a physical exam
  • Have you keep a detailed diary of the foods you or your child eats
  • Have you eliminate milk from your diet or your child’s diet (elimination diet) — and then have you add back the food to see if it causes a reaction

He or she may also recommend one or both of the following tests:

  • Skin test. In this test, your skin is pricked and exposed to small amounts of the proteins found in milk. If you’re allergic, you develop a raised bump (hive) at the test location on your skin. Allergy specialists usually are best equipped to perform and interpret allergy skin tests. This type of test isn’t always accurate for detecting milk allergy.
  • Blood test. A blood test can measure your immune system’s response to milk by measuring the amount of immunoglobulin E (IgE) antibodies in your blood. This test isn’t always accurate in identifying a milk allergy.

If your examination and test results can’t confirm a milk allergy, your doctor might administer an oral challenge, in which you are fed different foods that may or may not contain milk in increasing amounts to see if you react to the ones that contain milk. Allergy tests are best administered by an allergist who’s trained to manage serious reactions.

If your doctor suspects your symptoms are caused by something other than a food allergy, you may need other tests to identify — or rule out — other medical problems. 


If you are diagnosed with a food, or specifically milk or casein, allergy, your doctor may advise you carry injectable of 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, the antihistamine will not act as rapidly or as effectively as epinephrine. Epinephrine 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, then 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 many 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, 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.
  • 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.
  • 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. 

Useful advice

What does the casein-free diet entail?

Casein protein is closely related to gluten and so references to ‘gluten free, casein free diets’ are readily available online.

As casein is in all types of milk, a casein-free diet is essentially a dairy-free diet. Any milk-containing product should be avoided, including all the usual suspects: cream, yogurt, sour cream, cheese (unless it’s made from soy), butter, ice-cream, custard, creamed soups, soup bases and lots of sauces, like mayonnaise. Some margarines and even ‘dairy-free’ cheeses still contain casein, and some tuna-fish brands also list it in their ingredients. Ghee, which is used in lots of Indian cooking, can also contain casein. Many processed foods like sausages, hot dogs and lunch meat use it as a binding agent. Be careful buying meat from deli-counters as slicers are often used for both meat and cheese without being cleaned in between. Both milk and white chocolate should be avoided for obvious reasons (dark chocolate is fine, but watch out of ‘semi-sweet’ brands!). Casein is also in lots of artificial flavourings and additives so they are best avoided. Those that don’t contain casein include: all aluminium compounds, artificial colours and FD&C colours, aspartame (nutrasweet),  BHA ,  BHT, caffeine, EDTA,  monosodium Glutamate (MSG), nitrites and nitrates, olestra, saccharin, sulfites and vanillin… but, to be honest, they are best avoided anyway.

A note on labelling and eating out.

In the United States, manufacturers must list potential allergens on the packaging, and you will see statements such as ‘contains milk ingredients’ or ‘processed in a facility that also produces milk ingredients’ on the label. Many international brands adhere to this guideline globally – don’t rely on it though! Avoid anything with ‘milk’ or ‘butter’ in the ingredients list. Even if a product is labelled ‘dairy-free’, it still may not be casein-free. Read ingredients labels carefully so as not to be caught out. Casein can be listed as milk protein or as caseinates (e.g. rennet casein, calcium caseinate, casein hydrolysate, magnesium caseinate and sodium caseinate). Ingredients like this are often listed on energy bars, drinks, and packaged goods.

It’s also helpful to know that if a brand is labelled as ‘Kosher’ it is generally safe to consume. If a product contains neither meat or dairy it is listed a ‘Pareve’ under Jewish dietary laws. However, under these rules, the product may still contain small amounts of milk, so may contain enough casein protein to potentially provoke a reaction in an allergic individual.

It is a good idea to generally avoid battered foods when eating out, as the batter may contain milk. Avoiding fried foods generally is a good idea when eating out as the oil may have been used previously to fry something containing milk and even a trace amount may provoke an allergic reaction. Some dishes that may not seem to contain dairy on the menu in fact often do. For example, lots of restaurants will add butter to a grilled steak after it’s cooked to add flavour, and the butter melts in and becomes invisible. It’s a good idea to let your waiter or waitress know you are allergic to milk or dairy in general and discuss your menu choices with them before you order.

Some casein-free alternatives.

There are some great milk-free substitutes out there. Vegetable margarine can easily be used to replace butter for cooking, baking, or as a spread. Do check the labels, however, as some margarine brands still contain milk ingredients, which it is safe to assume contain casein. A good alternative to cow’s milk is soymilk, but there are also rice and potato-based milks out there. Coconut milk and butter are both fine and there are vegan cheeses that are soy-based. Soy ice-cream, dairy-free sorbets and Italian ices are all a delicious alternative to traditional dairy ice-creams, but again, don’t forget to check if casein has been added as a clotting agent on the ingredients list. Ghee is normally safe as well, as long as it is guaranteed casein-free on the label.

What are the benefits of a casein-free diet?

Going on a casein-free diet has obvious advantages if you have a milk-allergy and symptoms will clear up quickly once the substance is eliminated from the diet.

Gluten-free/casein-free diets are often recommended as an alternative therapy for the treatment of Autism. However, although studies have shown the benefits in these exclusion diets in treating symptoms , the studies themselves were not conclusive. Studies on animals have found a correlation between the amount of casein protein in diets and cancerous cell growth. It has also been shown that caseinate salts effect the bioavailability of some drugs, such as phenytoin, a medication often prescribed for seizures. Avoiding casein is a good idea for anyone on this medication.

As a casein-free diet is essentially also dairy-free, we shouldn’t underestimate the advantages of cutting dairy out of the diet. Although concerns over pasteurized, homogenized, pesticide and hormone ridden milk can be overcome by the consumption of raw, whole, organic milk and dairy, it is also important to examine dairy consumption from an evolutionary perspective. Dairy wasn’t a normal part of human diet until the domestication of animals 10,000 years ago.  Most humans stop producing lactase (the enzyme needed to break down lactose) during early childhood. If you are lactose intolerant, or have irritable bowel syndrome that is triggered by milk products, cutting dairy out of your diet will quickly alleviate your symptoms.

A massive benefit of eating dairy-free is that you are cutting out a lot of saturated fat from your diet: one of the major causes of heart disease. Proponents for the consumption of dairy as part of a healthy, balanced diet cite it as an important source of calcium, historically believed to be essential for healthy bones. However, studies have shown that a high calcium intake doesn’t necessarily lower the risk of osteoporosis or bone fractures. Vitamin D (found in oily fish, eggs and fortified breakfast cereals), which aids in the absorption of calcium, is emerging as just as essential for healthy bones.

Some people argue that dairy products are acid forming after being metabolised, forcing the body to battle harder to retain its delicately balanced blood pH level of 7.35-7.45. One of the mechanisms our bodies use to do this is through the release of calcium from our bones (which is ideally then replaced). Proponents of the alkalizing diet will argue that, because of this, consumption of dairy actually weakens bones rather than strengthens them, and researchers have argued that the animal protein in dairy causes bone loss. Furthermore, there are more effective and nutritious ways of ensuring your body has the correct level of calcium and vitamin D than by consuming dairy.

In children, there is evidence that links incidents of anaemia with a high dairy intake. Dairy is also suspected of aggravating allergies and congestion problems like sinusitis and ear infections, as well as chronic constipation. Type 1 diabetics are advised to avoid it completely.

What are the potential disadvantages of a casein-free diet?

Studies have shown that a moderate consumption of calcium via dairy can reduce the risk of colon cancer, although high consumption doesn’t seem to reduce it even further. Excluding casein-containing dairy products from the diet can limit one of the major sources of calcium and vitamin D from the diet. However, it is unclear what the optimal method is for the consumption and absorption of calcium so cutting dairy out of your diet doesn’t necessarily lead to calcium deficiency. There are plenty of supplements out there and it is easy to subsidise your calcium intake by eating foods naturally high in calcium.

As casein allergies are much more prevalent in children, it is doubly important to ensure that other sources of vitamin D, essential for the absorption of calcium and for healthy bone growth, are included in the diet. Many people take supplements, but lots of casein free alternatives like soy-based cheeses are already enriched with both vitamin D and calcium. Green, leafy vegetables like kale are also naturally high in calcium, as are herbs, nuts and seeds… and fish like herring have high levels of vitamin D. Milk and dairy are also a source of protein and vitamin A, but both of these nutritional essentials are easily sourced elsewhere. 


The symptoms of casein allergy can range from mild to life threatening. If a food or ingredient is easy to avoid, the allergy may interfere very little with daily life. Some foods and ingredients, however, are widespread, and avoiding them will involve careful monitoring. Some food allergies disappear as a child ages. 


Children who are allergic to casein are more likely to develop certain other health problems, including:

  • Allergies to other foods — such as eggs, soy, peanuts or even beef
  • Hay fever — a common reaction to pet dander, dust mites, grass pollen and other substances


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