Why do people get allergies?

People are said to have allergies when their bodies have a negative reaction to a foreign substance.

According to the Mayo Clinic, antibodies protect us from unwanted bacteria that could cause infection. When a person has allergies, their antibodies are reacting to a substance that it thinks is harmful, even when it isn’t.

Some common allergens are foods (like peanuts, shellfish, and dairy products), medications and insect stings.