The most critical symptom of dairy allergies, particularly milk allergies, is anaphylaxis, as stated by the Center for Young Women's Health. This symptom could potentially prove fatal if emergency treatment is not administered.
Dairy allergies occur when a person's immune system induces an adverse reaction to proteins found in dairy products, specifically the milk protein content in these products. In people with milk allergies, ingestion of these substances may trigger the onset of hives, rashes, sneezing, wheezing and asthma. Inflammation of the lips, tongue, mouth or throat is also a common occurrence in milk allergies.
Anaphylaxis is an acute immune response that alters normal body functions. A person that goes into an anaphylactic shock may experience difficulty in breathing, reduced blood pressure, lightheadedness and a fainting sensation, according to the American College of Allergy, Asthma & Immunology. Epinephrine is the only treatment for this condition.