Acute Care Nurse Practitioner Certification 2025 – 400 Free Practice Questions to Pass the Exam

An allergic reaction is primarily defined as a hypersensitivity reaction to an allergen, which is a substance that typically does not cause a reaction in most individuals but triggers an immune response in sensitized individuals. This immune response can involve the production of immunoglobulin E (IgE) antibodies, which bind to allergens and cause various cells, such as mast cells and basophils, to release histamine and other chemicals. This release leads to the typical symptoms of an allergic reaction, which can range from mild symptoms, such as sneezing and nasal congestion, to severe reactions, including anaphylaxis.

The other options describe conditions or symptoms that do not encompass the comprehensive definition of an allergic reaction. For instance, severe headache and fatigue could indicate various medical conditions or stress but are not specific to allergic responses. Similarly, respiratory symptoms, while common in allergic reactions such as in asthma or rhinitis, do not account for the full spectrum of symptoms that can arise from an allergy. Lastly, cognitive disruptions do not relate to allergic responses and are more associated with psychological or neurological conditions rather than hypersensitivity to allergens. Therefore, the definition of allergic reaction as a hypersensitivity reaction to an allergen is accurate and encompasses the mechanisms and systemic effects involved.