Food allergy: An allergic reaction to a food triggered by the immune system. It can cause serious health problems and even death. Note: If you have a food allergy and emergency epinephrine (adrenalin) is recommended by your doctor, keep it with you at all times. Wear a medical alert bracelet or carry information that identifies your food allergies.

Food intolerance: An adverse reaction to a food that leads to unpleasant, but not life-threatening, symptoms. It does not involve an immune system reaction.

-Mayo Clinic-