Because both are triggered by milk, a milk allergy is often confused with milk intolerance (or lactose intolerance), which is not an allergy. An allergy always involves an exaggerated response by the immune system to a substance that, in most people, does not cause a reaction.

Milk intolerance is a sensitivity to the sugar found in milk products (lactose). In people with this condition, the small intestine is unable to produce enough of a specific enzyme (lactase) to break lactose down for easy digestion. The result of the undigested lactose is symptoms of diarrhea, gas and abdominal cramps. Symptoms of milk intolerance generally involve discomfort, but pose little risk. Milk allergy reactions, however, are potentially life-threatening. Some individuals with milk intolerance can tolerate some forms of dairy, whereas people with a milk allergy must avoid dairy completely.

Food poisoning can also be mistaken for a milk allergy because it can produce the same symptoms. Food poisoning occurs when an individual consumes food that is contaminated with microorganisms such as bacteria. Consuming contaminated milk can cause gastrointestinal symptoms such as nausea, vomiting, abdominal cramps and diarrhea.

Because individuals with a milk allergy must completely remove milk and dairy products from their diets, a calcium deficiency can result. This condition causes bone weakening and skeletal abnormalities. Fortunately, regular supplements or dietary additions can replace the missing calcium. Foods such as fish and vegetables can also help replace calcium. A physician can help evaluate a milk allergic individual’s diet and suggest an appropriate kind of calcium supplement.

A latex allergy can share the symptoms of a milk allergy, occasionally complicating a milk allergy diagnosis. While both are true allergies that involve an immune system reaction, latex allergies are typically triggered by external contact with latex, which is the flexible, elastic material used in many rubber products. Latex allergies can also be triggered by inhaling latex particles that have become airborne.