Which assessment finding would most likely indicate anaphylaxis?

A sudden drop in blood pressure is a hallmark indicator of anaphylaxis, which is a severe and potentially life-threatening allergic reaction. Anaphylaxis triggers the release of large amounts of histamine and other chemicals into the bloodstream, leading to extensive vasodilation, increased vascular permeability, and ultimately a significant drop in blood pressure.

In this context, the body is attempting to cope with the rapid onset of hypersensitivity to substances—commonly allergens such as certain foods, insect stings, or medications—resulting in symptoms like the sudden drop in blood pressure. This drastic change can lead to shock, which requires immediate medical intervention to reverse the reaction and stabilize the patient.

Other symptoms associated with anaphylaxis include difficulty breathing, swelling of the throat or tongue, rapid heart rate, and skin reactions such as hives. While rash with itching can also be a sign from an allergic reaction, it is not as critical as the drop in blood pressure, which directly indicates systemic involvement. Severe headache and fever are more indicative of other conditions, such as infections or migraines, and are not classic symptoms of anaphylaxis.