True food allergies involve our body's immune system. Eight foods account for over 90 percent of all food allergies: peanuts, tree nuts, wheat, milk, eggs, soy, fish and shellfish.
After consuming the offensive food (protein), or "allergen," the body responds by releasing antibodies, and histamine to fend off the "foreign" invader. Symptoms may include: hives, rash, difficulty breathing, tingling sensation in the mouth, swelling of the tongue or throat, diarrhea, nausea, and a drop in blood pressure.
A food intolerance does not involve the immune system. Lactose intolerance, for example, results from the body's inability to digest milk sugar. It results in gas and bloating. It's uncomfortable, but it's not life threatening. (14,15)