Cow’s milk is one of the most common allergy-causing foods in children, and it’s the leading cause of allergic reactions in very young children. Milk allergy affects about 2 percent to 3 percent of infants worldwide, and its signs and symptoms can be serious enough to cause distress not just for an allergic child, but also for the child’s family. Most children outgrow a milk allergy by age 2 or 3. It’s important to differentiate a true milk allergy 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 than does a true milk allergy. Common signs and symptoms of milk protein or lactose intolerance include digestive problems, such as bloating, gas or diarrhea, after consuming milk.
Rarely, milk allergy can cause anaphylaxis, a life-threatening reaction that can constrict the airways and block breathing. If you or your child has a reaction to milk, tell your doctor about it no matter how mild the reaction may have been. Tests can help confirm a milk allergy, so you can take steps to 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
- Shock, with a severe drop in blood pressure
- Rapid pulse
- Dizziness, lightheadedness or loss of consciousness
Signs and symptoms of milk allergy differ from person to person and occur within a few minutes to a few hours after ingesting milk. In some cases, reactions to a milk allergy develop after exposure to milk for an extended period of time. Rarely, infants have an allergic reaction to small amounts of cow’s milk protein passed through their mother’s breast milk. Signs of a milk allergy that may occur immediately after consuming milk include:
Signs and symptoms that may take more time to develop include:
- Loose stools (which may contain blood or mucus)
- Abdominal cramps
- Coughing or wheezing
- Runny nose
- Skin rash
All 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, these IgE antibodies recognize them and signal your immune system to release histamine and other chemicals. Histamine and other body chemicals cause a range of allergic signs and symptoms. Histamine is partly responsible for most allergic responses, including runny nose, itchy eyes, dry throat, rashes, hives, nausea, diarrhea, labored breathing and anaphylactic shock.
There are two types of protein in milk that can cause an allergic reaction:
- Casein, which is found in the solid part (curd) of milk that curdles
- Whey, which is 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 allergic to both casein and whey. These proteins are not only present in milk — but also are found in many processed foods. Certain foods contain both casein and whey; other foods contain only one allergy-causing milk protein.
Certain factors may put you at greater risk of developing a milk allergy:
Other allergies. Many children allergic to milk develop other allergies. Often, milk allergy is the first to develop — but sometimes others appear first.
Atopic dermatitis. Children with this type of skin reaction are much more likely to develop a food allergy.
Family history. You’re at increased risk of a food allergy if one or both of your parents have a food allergy or another type of allergy — such as hay fever, asthma, hives or eczema.
Age. Milk allergy is most common in children. As you grow older, your digestive system matures and your body is less likely to absorb food or food components that trigger allergies.
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
Doctor 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 a milk allergy.
- Blood test. A blood test can measure your immune system’s response to milk by measuring the amount of certain antibodies in your bloodstream, known as immunoglobulin E (IgE) antibodies. A blood sample is sent to a medical laboratory, where it can be tested for evidence of sensitivity to milk.
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.
Children who are allergic to milk are much more likely to develop certain other health problems, including:
- Allergies to other foods — such as eggs, soy or peanuts
- Hay fever — a reaction to pet dander, dust mites, grass pollen and other substances
- Gastroesophageal reflux disease (GERD), a type of heartburn in which stomach acid or bile flows back (refluxes) into the esophagus
The only way to prevent an allergic reaction is to avoid milk and milk proteins altogether. This can be difficult, as milk is a common food ingredient. Despite your best efforts, you or your child may still come into contact with milk. Medications, such as antihistamines, may reduce signs and symptoms of a milk allergy. These drugs can be taken after exposure to milk to control an allergic reaction and help relieve discomfort. If you or your child has a serious allergic reaction (anaphylaxis), you may need an emergency injection of epinephrine (adrenaline) and a trip to the emergency room. If you’re at risk of having a severe reaction, you or your child may need to carry injectable epinephrine (such as an EpiPen) at all times. There is no sure way to prevent a food allergy from occurring in the first place — but you can prevent signs and symptoms by avoiding the food that causes them. If you know you or your child is allergic to milk, the only sure way to avoid an allergic reaction is to avoid milk products. Know what you or your child is eating and drinking. Be sure to read food labels carefully.
Some research suggests that you shouldn’t give your child cow’s milk or cow’s milk products until age 1 — the idea is that this may help prevent your child from developing a milk allergy. However, this idea hasn’t yet been proved to work, and isn’t recommended by all experts. 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. Experts recommend breast-feeding for at least the first six months of life if possible. Breast-feeding may reduce your baby’s chance of developing a milk allergy. Your doctor may also recommend eliminating cow’s milk from your diet while nursing your baby.
- 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. These are also called elemental formulas. Some hypoallergenic formulas aren’t milk based, but instead contain amino acids. Along with 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, many children with a milk allergy develop an allergy to soy.
- Meat-based formulas can be made at home with pureed beef, turkey, lamb or other meats.
Milk from goats or sheep isn’t a workable substitute for cow’s milk, as these types of milk contain proteins similar to the allergy-causing proteins in cow’s milk.
If you are breast-feeding and your child has a milk allergy, cow’s milk proteins passed through your breast milk may cause an allergic reaction. If this is the case, 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 has allergy signs and symptoms that occur 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.
Allergic to whey? Some milk products may be OK
Some people with milk allergies can consume certain milk products that have been processed. Whether you or your child can tolerate certain milk products depends on what protein is causing the reaction. If you have an allergy caused by casein, you probably will react to all milk products. If you are allergic to whey, you may be able to tolerate certain milk products:
- Cheese. Harder cheeses, which contain more casein, may be less likely to cause a reaction if you have an allergy caused by whey.
- Milk that has been treated with high heat. This includes pasteurized milk as well as evaporated, powdered or long-life milk. High heat will reduce — but not completely eliminate — allergy-causing whey proteins in milk.
Hidden sources of milk products
Allergy-causing milk proteins are found in dairy products, such as yogurt, cheese, butter, half-and-half and sour cream. But milk can be harder to identify when it’s used as an ingredient in processed food products ranging from sausage to breakfast cereals. Hidden sources of milk include:
- Ingredients that contain the prefix “lact” — such as lactose and lactate
- Candies, such as chocolate, nougat and caramel
- Fat-replacement products, such as Simplesse
- Protein powders
- Artificial butter flavor
- Artificial and natural flavorings — used in products ranging from canned fish to potato chips
Even if a food is labeled “milk-free” or “nondairy,” it may still 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.
While there is no sure way to prevent an allergic reaction to milk, reading labels, being cautious when eating out and using hypoallergenic or milk-free products can help you or your child avoid an unpleasant or dangerous reaction. 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 that you have a food allergy.