Cow's milk is the usual cause, but milk from sheep, goats, buffalo and other mammals also can cause a reaction. An allergic reaction usually occurs minutes to hours after consuming milk. Signs and symptoms of milk allergy range from mild to severe and can include wheezing, vomiting, hives and digestive problems. Sometimes, milk allergy can cause anaphylaxis — a severe, life-threatening reaction. Avoidance is the primary treatment for milk allergy. Fortunately, most children outgrow a milk allergy.