The answer to this question comes down to the difference between an allergy and intolerance. An allergy is an immune hypersensitivity to a particular allergen, and usually causes an immediate reaction that typically includes itching and may include other symptoms, such as difficulty breathing, swelling, low blood pressure, and hives. People who are allergic to a food cannot ingest even small amounts of the food without risking an allergic reaction. Those who are allergic often will have a positive skin or blood test when given a small amount of the food. This type of person will need to be careful to avoid all forms of such food. This is different from intolerance, which means your body does not easily or effectively process the food. Intolerance can lead to gastrointestinal symptoms, such as bloating, abdominal pain and sometimes vomiting or diarrhea. People who have lactose intolerance will have a negative skin test to milk and often can tolerate small amounts of dairy products and normal amounts of lactose-free dairy products. They are not at increased risk of having a severe allergic reaction with eating dairy, but simply may not feel good.