A milk allergy is a potentially deadly allergic reaction to one or more dairy proteins. It is one of the eight food allergies that make up 90 percent of all known food allergies, according to the Food Allergy and Anaphylaxis Network (FAAN ). The only way to successfully treat a milk allergy is to completely remove milk and dairy products from the diet.

It is important to note that a milk allergy is not the same as a milk intolerance, a sensitivity to the sugar found in milk products which does not involve the immune system and is usually less severe.

Milk allergies are most common in young children, who usually develop the condition within the first six months of life. According to the Asthma and Allergy Foundation of America, studies have shown that 2 to 5 percent of children develop a milk allergy in the first year of life. Parents usually discover that an infant has a milk allergy when the child has a reaction to baby formula.

According to the American Academy of Pediatrics, 70 to 80 percent of infants with milk allergies outgrow the condition by the age of 4. However, some milk allergy conditions persist throughout adulthood. It is rare for an adult to develop a milk allergy.

An allergic reaction to milk occurs when one of the milk proteins makes its way into the body of an allergic individual. This usually occurs when the protein is consumed, though it can also occur when an individual absorbs milk protein through the skin (some latex gloves contain milk protein). Once the protein is inside the person’s body, an allergic cascade is triggered as the immune system misinterprets the protein as a dangerous substance.

The immune system produces specific milk IgE antibodies that appear in the bloodstream. These antibodies bind to body cells (mast cells and basophils). The next time IgE antibodies come in contact with the offending milk protein, histamines and other chemicals are released into the blood, which stimulates allergy symptoms.   

Symptoms may range from mild anaphylaxis (generalized reaction involving two or more body systems) to life-threatening anaphylactic shock, which involves breathing problems and lowered blood pressure.

The symptoms of a milk allergy usually occur in one of two different ways. These include:

• Rapid onset. This type of reaction usually occurs suddenly, often only a few minutes after consuming a milk protein. Anaphylaxis symptoms can occur swiftly and severely with this type of reaction, and it can be fatal if not properly treated.
  
  
• Slower onset. This is the most common type of reaction to a milk protein. This reaction often occurs several hours after ingesting milk. Symptoms usually involve the gastrointestinal system.

There are some alternatives to milk and dairy products. Soybeans, tofu, rice milk and soy milk can often be used in the place of milk or dairy products, and can also be good sources of calcium. About 10 percent of individuals with a milk allergy can tolerate milk from sheep or goats. However, because goat's milk and sheep's milk share common allergens or cross re-act with cow's milk, individuals should initially try these alternatives only under a physician’s supervision.

Milk allergies are often passed on genetically, meaning a child that comes from a family with a history of allergies – particularly a food allergy – is more likely to have a milk allergy. Families that have a history of allergic rhinitis (hay fever), eczema (inflammatory skin disease with lesions that usually appear very dry, thickened or scaly) and other allergies all have an increased risk of producing children with allergies.

A recent study also suggests that method of birth may play a role in a child's reaction to milk. Children delivered by Cesarean section (a procedure in which a baby is delivered through an incision in the mother's abdomen) appear to be twice as likely to develop a milk allergy or milk intolerance.

The signs and symptoms of milk allergies are the same as other food allergies. The most common symptoms include:

• Wheezing (a whistling or high-pitched sound that results when breathing tubes are narrowed or obstructed)
  
  
• Hives (smooth, raised pink or white bumps that appear on or beneath the skin)
  
  
• Skin rash
  
  
• Eczema
  
  
• Nausea
  
  
• Vomiting
  
  
• Diarrhea
  
  
• Swelling (around them mouth and lips)
  
  
• Abdominal cramps
  
  
• Bloated sensation
  
  
• Asthma (a chronic inflammation of the bronchial [airway] tissues that produces shortness of breath, chest tightness, coughing and wheezing)