Milk allergy is an abnormal response by the body’s immune system to milk and products containing milk. Cow’s milk is the usual cause of milk allergy, but milk from sheep, goats and buffalo also can cause a reaction. Some children who are allergic to cow’s milk are allergic to soy milk, too. Milk allergy is one of the most common food allergies in children.
A milk allergy 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. Rarely, 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 by age 3.
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:
Signs and symptoms that may take more time to develop include:
Loose stools, which may contain blood
Coughing or wheezing
Itchy skin rash, often around the mouth
Colic, in babies
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, 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, difficulty breathing and anaphylactic shock.
There are two main proteins in cow’s 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 not only are present in milk, but they’re also found in processed foods. Additionally, most people who react to cow’s milk will also be allergic to sheep, goat and buffalo milk. Less commonly, people allergic to cow’s milk are also allergic to soy milk.
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, peanuts or even beef
Hay fever — a reaction to pet dander, dust mites, grass pollen and other substances
The only way to prevent an allergic reaction is to avoid milk and milk proteins altogether. This can be difficult because milk is a common ingredient in many foods. Despite your best efforts, you or your child may still come into contact with milk. If this happens, medications, such as antihistamines, may reduce signs and symptoms of a mild milk allergic reaction. These drugs can be taken after exposure to milk to control an allergic reaction and help relieve discomfort. Talk with your doctor about which medications might work best for you.
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. Have your doctor or pharmacist demonstrate how to use this device so you’re prepared for an emergency.
Allergy shots, also sometimes called immunotherapy, haven’t been proved effective for treating food allergies, but research is ongoing.
There’s no sure way to prevent a food allergy, 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. Look for casein, a milk derivative, which can be found in some unexpected places, such as in some canned tuna or other meats. Ask questions about ingredients when ordering in restaurants.