Final answer:
Food allergies occur when the immune system reacts to substances in food as though they were harmful "foreign invaders." Some common allergenic foods include nuts, eggs, grains, milk, and shellfish.
Step-by-step explanation:
Food allergies occur when the immune system reacts to substances in food as though they were harmful "foreign invaders." Some of the foods that commonly cause allergies include nuts, eggs, grains, milk, and shellfish.