Overview

Milk allergy, one of the most common food allergies in children, is an abnormal response by the body's immune system to milk and products containing milk. Cow's milk is the usual cause, but milk from sheep, goats, buffalo and other mammals also can cause a reaction.

An allergic reaction usually occurs minutes to hours after consuming milk. Signs and symptoms of milk allergy range from mild to severe and can include wheezing, vomiting, hives and digestive problems. Sometimes, milk allergy can cause anaphylaxis — a severe, life-threatening reaction.

Avoidance is the primary treatment for milk allergy. Fortunately, most children outgrow a milk allergy. Those who don't outgrow it may need to continue to avoid milk products.

Symptoms

Milk allergy symptoms, which differ from person to person, occur a few minutes to a few hours after drinking milk or eating milk products.

Immediately after consuming milk, signs and symptoms of a milk allergy might include:

  • Hives
  • Wheezing
  • Vomiting

Signs and symptoms that may take more time to develop include:

  • Loose stools, which may contain blood
  • Diarrhea
  • Abdominal cramps
  • Coughing or wheezing
  • Runny nose
  • Watery eyes
  • Itchy skin rash, often around the mouth
  • Colic, in babies

Milk allergy or milk intolerance?

A true milk allergy differs from milk protein intolerance or lactose intolerance. Unlike a milk allergy, intolerance doesn't involve the immune system. Milk intolerance causes different symptoms and requires different treatment from a true milk allergy.

Common signs and symptoms of milk protein intolerance or lactose intolerance include digestive problems, such as bloating, gas or diarrhea, after consuming milk or products containing milk.

Anaphylaxis

Milk allergy can cause anaphylaxis, a life-threatening reaction that can narrow the airways and block breathing. Milk is the third most common food, after peanuts and tree nuts, to cause anaphylaxis.

If you or your child has a reaction to milk, tell your doctor, no matter how mild the reaction. Tests can help confirm a milk allergy, so you can avoid future and potentially worse reactions.

Anaphylaxis is a medical emergency and requires treatment with an epinephrine (adrenaline) shot and a trip to the emergency room. Signs and symptoms start soon after consuming milk and can include:

  • Constriction of airways, including a swollen throat that makes it difficult to breathe
  • Facial flushing
  • Itching
  • Shock, with a marked drop in blood pressure

When to see doctor

See your doctor or an allergist if you or your child experiences milk allergy symptoms shortly after consuming milk. If possible, see your doctor during the allergic reaction to help the doctor make a diagnosis. Seek emergency treatment if you or your child develops signs or symptoms of anaphylaxis.

Causes

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 milk 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.

Complications

Children who are allergic to milk 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

Prevention

There's no sure way to prevent a food allergy, but you can prevent reactions by avoiding the food that causes them. If you know you or your child is allergic to milk, avoid milk and milk products.

Read food labels carefully. Look for casein, a milk derivative, which can be found in some unexpected places, such as in some canned tuna or nondairy products. Question ingredients when ordering in restaurants.

Sources of milk products

Obvious sources of allergy-causing milk proteins are found in dairy products, including:

  • Whole milk, low-fat milk, skim milk, buttermilk
  • Butter
  • Yogurt
  • Ice cream, gelato
  • Cheese and anything that contains cheese
  • Half-and-half

Milk can be harder to identify when it's used as an ingredient in processed foods, including baked goods, processed meats and breakfast cereals. Hidden sources of milk include:

  • Whey
  • Casein
  • Ingredients spelled with the prefix "lact" — such as lactose and lactate
  • Candies, such as chocolate, nougat and caramel
  • Protein powders
  • Artificial butter flavor
  • Artificial cheese flavor
  • Hydrosolate

Even if a food is labeled "milk-free" or "nondairy," it may contain allergy-causing milk proteins — so you have to read the label carefully. When in doubt, contact the manufacturer to be sure a product doesn't contain milk ingredients.

When eating out, ask how foods have been prepared. Does your steak have melted butter on it? Was your seafood dipped in milk before cooking?

If you're at risk of a serious allergic reaction, talk with your doctor about carrying and using emergency epinephrine (adrenaline). If you have already had a severe reaction, wear a medical alert bracelet or necklace that lets others know you have a food allergy.

Milk alternatives for infants

Some research suggests that breast-feeding during the first four to six months of a baby's life instead of giving a standard cow's milk formula can help prevent milk allergy. In children who are allergic to milk, breast-feeding and use of hypoallergenic formula can prevent allergic reactions.

  • Breast-feeding is the best source of nutrition for your child. Breast-feeding for at least the first four to six months of life if possible is recommended, especially if your infant is at high risk of developing a milk allergy.
  • Hypoallergenic formulas are produced by using enzymes to break down (hydrolyze) milk proteins, such as casein or whey. Further processing can include heat and filtering. Depending on the level of processing, products are classified as either partially or extensively hydrolyzed. Or they may also be called elemental formulas.

    Some hypoallergenic formulas aren't milk based, but instead contain amino acids. Besides extensively hydrolyzed products, amino-acid-based formulas are the least likely to cause an allergic reaction.

  • Soy-based formulas are based on soy protein instead of milk. Soy formulas are fortified to be nutritionally complete — but, unfortunately, some children with a milk allergy also develop an allergy to soy.

If you're breast-feeding and your child has a milk allergy, cow's milk proteins passed through your breast milk may cause an allergic reaction. Then you may need to exclude all products that contain milk from your diet. Talk to your doctor if you know — or suspect — your child has a milk allergy and develops allergy signs and symptoms after breast-feeding.

If you or your child is on a milk-free diet, your doctor or dietitian can help you plan nutritionally balanced meals. You or your child may need to take supplements to replace calcium and nutrients found in milk, such as vitamin D and riboflavin.