Milk allergy is an abnormal response by the body's immune system to milk and products containing milk. It's one of the most common food allergies in children. Cow's milk is the usual cause of milk allergy, but milk from sheep, goats, buffalo and other mammals also can cause a reaction.
An allergic reaction usually occurs soon after you or your child consumes milk. Signs and symptoms of milk allergy range from mild to severe and can include wheezing, vomiting, hives and digestive problems. Milk allergy can also cause anaphylaxis — a severe, life-threatening reaction.
Avoiding milk and milk products is the primary treatment for milk allergy. Fortunately, most children outgrow milk allergy. Those who don't outgrow it may need to continue to avoid milk products.
Milk allergy symptoms, which differ from person to person, occur a few minutes to a few hours after you or your child drinks milk or eats milk products.
Immediate signs and symptoms of milk allergy might include:
- Itching or tingling feeling around the lips or mouth
- Swelling of the lips, tongue or throat
- Coughing or shortness of breath
Signs and symptoms that may take more time to develop include:
- Loose stools or diarrhea, which may contain blood
- Abdominal cramps
- Runny nose
- Watery eyes
- Colic, in babies
Milk allergy or milk intolerance?
A true milk allergy differs from milk protein intolerance and lactose intolerance. Unlike milk allergy, intolerance doesn't involve the immune system. Milk intolerance requires different treatment from 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.
Milk allergy can cause anaphylaxis, a life-threatening reaction that narrows the airways and can 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 milk allergy, so you can avoid future and potentially worse reactions.
Anaphylaxis is a medical emergency and requires treatment with an epinephrine (adrenaline) shot (EpiPen, Adrenaclick, others) and a trip to the emergency room. Signs and symptoms start soon after milk consumption and can include:
- Constriction of airways, including a swollen throat that makes it difficult to breathe
- Facial flushing
- 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.
All true food allergies are caused by an immune system malfunction. If you have milk allergy, 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 to 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 within minutes.
Unlike some food allergies, FPIES usually resolves over time. As with milk allergy, preventing an FPIES reaction involves avoiding milk and milk products.
Certain factors may increase the risk of developing milk allergy:
- Other allergies. Many children allergic to milk also have other allergies. Milk allergy may develop before other allergies.
- 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 or allergic disease — such as hay fever, asthma, hives or eczema.
- Age. Milk allergy is more common in children. As they age, their digestive systems mature, and their bodies are less likely to react to milk.
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
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, sausage or nondairy products. Question ingredients when ordering in restaurants.
Sources of milk
Obvious sources of allergy-causing milk proteins are found in dairy products, including:
- Whole milk, low-fat milk, skim milk, buttermilk
- Ice cream, gelato
- Cheese and anything that contains cheese
Milk can be harder to identify when it's used as an ingredient in processed foods, including baked goods and processed meats. Hidden sources of milk include:
- 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
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
In children who are allergic to milk, breast-feeding and the use of hypoallergenic formula can prevent allergic reactions.
- Breast-feeding is the best source of nutrition for your infant. Breast-feeding for as long as possible is recommended, especially if your infant is at high risk of developing 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 their 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 is allergic to milk, cow's milk proteins passed through your breast milk may cause an allergic reaction. You may need to exclude from your diet all products that contain milk. Talk to your doctor if you know — or suspect — that your child has 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.