Which symptoms are associated with an anaphylactic reaction?

A. Slow heart rate: Anaphylaxis is characterized by systemic vasodilation and increased vascular permeability due to massive histamine and mediator release from mast cells and basophils. The resulting hypotension typically triggers a compensatory tachycardia rather than bradycardia. A slow heart rate is not a typical early manifestation of an acute anaphylactic reaction. B. Hives and swelling: Urticaria (hives) and angioedema are hallmark features of anaphylaxis caused by histamine-mediated capillary leakage and vasodilation. These manifestations often appear rapidly after exposure to the triggering allergen and may involve the skin, lips, tongue, or airway. The swelling reflects increased vascular permeability and fluid shift into interstitial tissues. C. Bleeding: Anaphylaxis does not primarily affect coagulation pathways or platelet function. The reaction is mediated by immunoglobulin E–triggered mast cell degranulation, leading to inflammatory mediator release rather than hemorrhagic processes. Bleeding is not a characteristic feature of this hypersensitivity response. D. Skin necrosis: Skin necrosis involves tissue ischemia and cellular death, commonly associated with severe vascular compromise, infection, or extravasation injuries. Although anaphylaxis causes vasodilation and edema, it does not typically produce localized tissue death. The cutaneous findings are more commonly erythema, urticaria, and flushing.