Some young children develop an allergy to milk, with symptoms ranging from swelling of the eyes and face to nausea and difficulty breathing. Other children, as they mature, develop intolerance to lactose, the sugar found in milk, making it difficult for them to digest it.
Most children with a milk allergy will outgrow it between 5 and 8 years of age, according to the American Academy of Allergy, Asthma and Immunology (AAAAI). Children who develop milk intolerance will not outgrow it.
It is important to understand the difference between food allergy and food intolerance. A food allergy, or hypersensitivity, is an abnormal response to a food that is triggered by the immune system, the AAAAI says. The immune system is not responsible for the symptoms of food intolerance, even though the symptoms may resemble those of a food allergy.
Intolerance to a food may mean the body does not have an enzyme necessary to digest a particular part of the food. Food intolerance is not a life-threatening condition. With milk, it is the lactose that many people cannot digest.
When there is not enough lactase, an enzyme needed to digest the amount of lactose consumed, the results can be very distressing--stomach cramps, bloating, gas, and/or diarrhea.
Children and adults who develop milk intolerance fail to produce enough lactase. But over-the-counter pills can provide the missing enzyme. Milk intolerance is considered a mild, if annoying, problem.
Allergies and the immune system
A food allergy is an immune system response to a food that the body mistakenly believes is harmful. Once the immune system decides that a particular food is harmful, it creates specific antibodies to it. In milk—and all food allergies—the culprits are proteins.
The next time the person eats that food (and those proteins), the immune system releases massive amounts of chemicals, including histamine, to protect the body. These chemicals trigger a cascade of allergic symptoms that can affect the respiratory system, gastrointestinal tract, skin, or cardiovascular system, the AAAAI says. Symptoms may include a tingling sensation in the mouth, swelling of the tongue and throat, difficulty breathing, hives, vomiting, abdominal cramps, diarrhea, a drop in blood pressure, and loss of consciousness. Symptoms typically appear within minutes to two hours after the person has eaten the food to which he or she is allergic and can end in death, especially if not treated promptly.
The majority of children who are allergic to the proteins in cow's milk are also allergic to goat's and sheep's milk. Symptoms of milk allergy include a red, bumpy skin rash called hives; eczema; redness and swelling around the mouth; stomach cramps; loose stools, possibly with blood; nausea or vomiting; runny nose; congestion; watery eyes; sneezing; and coughing. Most children with a milk allergy have more respiratory and ear infections than children without the allergy.
All children with a milk allergy need to avoid milk.
Two types of hypoallergenic formulas are approved by the FDA for infants with a milk allergy. One is made from cow’s milk in which the proteins have been broken down into small particles; the other is made from amino acids, the building blocks of proteins.
Prevention through breastfeeding
One way to help prevent a milk allergy in children is to breastfeed. Breastfeeding reduces the risk of an allergic reaction to cow's milk, although it doesn't eliminate it completely, the AAAAI says. The protein in cow's milk consumed by the mother can find its way into the breast milk.
The Academy of Nutrition and Dietetics (AND), formerly the American Dietetic Association, recommends that babies be breastfed exclusively for four to six months and then breastfed while solid foods are introduced, for a total of at least 12 months.
Infants who are breastfed for that length of time seem to have a better chance of avoiding food allergies, the AND says.