The immune system is the body's defense against invaders such as bacteria, fungi, or the common cold virus. A food allergy occurs when the immune system identifies a protein in what you eat as an invader and responds by creating antibodies to fight it.

The difference between a food allergy and a sensitivity is the body's response. With a food allergy, the immune system triggers a reaction. With a food sensitivity or intolerance, the reaction is triggered by the digestive system.