What causes allergies in the immune system?

The immune system is designed to protect the body from harmful invaders such as bacteria and viruses. However, in the case of allergies, the immune system mistakenly identifies harmless substances—like pollen, dust mites, or certain foods—as threats. This overreaction triggers an inappropriate immune response, leading to the release of various chemicals, including histamines, which cause allergy symptoms such as sneezing, itching, and swelling.

The underlying mechanism of allergies involves a type of immune response known as hypersensitivity, where the immune system becomes overly sensitive to specific antigens. This results in inflammation and other allergic reactions that can affect an individual's quality of life. Therefore, the answer that identifies an overreaction of the immune system to normally harmless substances accurately captures the essence of what causes allergies.

Other options, while related to immune system function, do not specifically address the nature of allergic reactions. For instance, an underactive immune response would not cause allergies but rather lead to increased susceptibility to infections. A lack of exposure to pathogens might contribute to certain immune issues but is not a direct cause of allergies. Similarly, genetic mutations can affect immune cell functions in various ways, but they do not specifically describe the mechanism behind allergic reactions.