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Why do people have allergies?
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People develop allergies because their immune systems are not functioning properly. The immune system is a complex network of cells and tissues that protect the body from foreign invaders, such as bacteria and viruses. When someone has an allergy, their immune system reacts to a harmless substance in the environment, such as pollen, dust, or pet dander, by producing antibodies against it. These antibodies cause inflammation and other symptoms.