An immunologic response to milk consumption. Cow’s milk contains 30-35 g protein per liter. The main antigens are β-lactoglobulin, casein, α-lactalbumin, serum lactalbumin, and the immunoglobulins. β-Lactoglobulin and α-lactalbumin are referred to as the whey proteins. Casein and β-lactoglobulin are the most heat-resistant. Cow’s milk allergy is most frequently seen in babies. In 10% of the cases, the symptoms appear in the first week of life, 33% in the second to fourth week, and in 40% during the following months. The main symptoms are eczema and gastrointestinal complaints such as diarrhea, cramps, vomiting, and constipation. Also, rhinitis, asthma, and rash may develop. An often obvious feature is irritability and restlessness. If the diagnosis is cow’s milk allergy, a few alternatives for cow’s milk are available. Goat’s milk and soy milk are sometimes used as are synthetic formulas using purified proteins and/or amino acids.