What effect does an allergen have on the immune system?

An allergen causes the immune system to overreact because it is perceived as a threat, even though it is typically harmless to the body. In response to the presence of allergens, such as pollen, dust mites, or certain foods, the immune system activates and produces various immune responses, particularly the production of immunoglobulin E (IgE) antibodies. This overreaction can lead to symptoms like inflammation, swelling, and the release of histamines, which contribute to allergic reactions.

The immune system is designed to protect the body from actual threats, such as pathogens. However, in the case of allergens, the immune system misidentifies these harmless substances as dangerous, leading to unnecessary and sometimes severe responses. This heightened response can result in conditions such as allergic rhinitis, asthma, or anaphylaxis in extreme cases.

In contrast, other choices do not accurately represent the role of an allergen in immune responses. Strengthening the immune response would imply a beneficial adaptation, while suppression of immune function does not relate to allergies, which involve an increased response. Lastly, stating that an allergen has no effect dismisses the clear physiological reactions that occur during allergic responses.