What results from an exaggerated immune response to a foreign substance?

An exaggerated immune response to a foreign substance, often referred to as an allergic reaction, typically involves the release of histamines. Histamines are chemicals produced by the body during an immune response, and they play a key role in the symptoms associated with allergies, such as itching, swelling, and mucus production. When the immune system misidentifies a harmless substance as a threat, it triggers this intense reaction, leading to the release of histamines from mast cells. This response is associated with conditions like hay fever, asthma, and anaphylaxis. Understanding the role of histamines helps in recognizing the symptoms of allergies and the body’s defensive mechanisms in response to perceived dangers.