Milk is made up of water, protein, carbohydrates (a milk sugar called lactose), minerals, fats and other substances. Milk allergies occur when our bodies react to the proteins in cow's milk, casein and whey, treating them as a foreign substance.
Milk allergy symptoms, or lactose intolerance, may appear immediately or several hours after the intake of moderate to large amounts of cow's milk.
Mostly children suffer from milk allergies, but most of them get rid of it by the time they are six. Although whey proteins can be broken down by heat, casein proteins are heat-stable and that is why those who are allergic to the latter cannot tolerate any cow's milk, even when it is boiled.
The most common milk allergy symptoms are similar to those of other food allergies: nausea, vomiting, diarrhea and abdominal cramps, or symptoms involving the skin, such as urticaria, and eczema.
Milk allergy symptoms include chronic runny nose, coughing, ear infections, excessive colic, excoriated buttocks, failure to thrive, fluid behind ears, irritability, nasal stuffiness, rash, hives and eczema, recurrent "colds," sinusitis, recurrent bronchitis, recurrent diarrhea, vomiting, abdominal pain, and wet and wheezy chest.
Three patterns of milk allergy symptoms have been recognized.
In Type 1, milk allergy symptoms appear within minutes after the intake of small volumes of cow's milk. The reactions are visible mainly on the skin: eczema or urticaria, with or without respiratory or gastro-intestinal symptoms.
In Type 2, milk allergy symptoms start several hours after intake of modest volumes of cow's milk. The symptoms in such cases are usually vomiting and diarrhea.
In Type 3, milk allergy symptoms begin to appear after more than 20 hours, or even days after intake of large volumes of cow's milk. The principal symptom here is diarrhea, with or without respiratory or skin reactions.
These milk allergy symptoms are not restricted to those people experiencing a milk allergy.
One, who is familiar with food allergy symptoms, can notice that numerous foods share a variety of common symptoms, such as bloating, rash, and runny nose.
The diagnosis of milk allergy in infants may become easier if the milk energy symptoms started soon after the child began on milk formula. The diagnosis may also be easy if a person shows the same symptoms repeatedly after eating milk-containing food.
In older children and adults, the diagnosis is often difficult because milk is usually consumed with other food. Only the milk allergy symptoms that develop after a few minutes are likely to give a positive blood or skin test, as these detect IgE that is involved in the immediate-type reaction.