Milk allergies are an abnormal response by the body to milk protein. Lactose intolerance is the body's inability to digest lactose, the sugar in milk. Allergies to milk are rare, while lactose intolerance is not.

A food allergy is an abnormal response of the body's immune system to ordinarily harmless foods or ingredients -- in this case, milk protein. An estimated 1-3% of infants and young children have milk allergy, but usually outgrow it by two or three years of age.

If milk allergy is suspected, consult a board-certified allergist for diagnosis. Those diagnosed with milk allergy should avoid consuming dairy foods, and should consult with a registered dietitian about how to get adequate calcium in the diet. Dairy food consumption can resume when and if the allergy is outgrown.

Lactose intolerance refers to the symptoms experienced by individuals who have low levels of the enzyme (lactase) necessary to break down lactose, or milk sugar. Some who have low levels of lactase are unaware of it and never experience any symptoms. It is most prevalent in African Americans, Hispanics, Native Americans, and Asian Americans. Fewer Caucasians have a problem digesting milk sugar. Infants are born with high levels of lactase, enabling them to digest the lactose in human milk or formula.