Food allergies also can make someone feel ill. But some some also can cause a life-threatening reaction (called anaphylaxis).
A food intolerance means either the body can't properly digest the food that is eaten, or that a particular food might irritate the digestive system. Symptoms of food intolerance can include nausea, gas, cramps, belly pain, diarrhea, irritability, or headaches.
A food allergy happens when the body's immune system, which normally fights infections, sees the food as an invader. This leads to an allergic reaction — an immune system response in which chemicals like histamine are released in the body. The reaction can cause symptoms like hives, vomiting, belly pain, throat tightness, hoarseness, coughing, breathing problems, or a drop in blood pressure.
Even if previous reactions have been mild, someone with a food allergy is always at risk for the next reaction being life-threatening. Eating a microscopic amount of the food could lead to anaphylaxis. So anyone with a food allergy must avoid the problem food(s) entirely and always carry emergency injectable epinephrine.
People with food sensitivities, on the other hand, might be able to ingest a small amount of the bothersome food without a problem.