An allergic reaction is an abnormal response of which system?

An allergic reaction is primarily an abnormal response of the immune system. When the body encounters a substance that it identifies as a threat (allergen), such as pollen, certain foods, or medications, the immune system reacts by producing antibodies. These antibodies help identify and neutralize the allergen but can also lead to symptoms that include inflammation, itching, rashes, difficulty breathing, or even anaphylaxis in severe cases. The immune response can be disproportionate to the actual threat posed by the allergen, resulting in what is classified as an allergic reaction. This involvement of the immune system is key to understanding how allergies develop and the underlying mechanisms that trigger these potentially harmful responses.