What is the severe allergic reaction that affects multiple body systems called?

Anaphylaxis is the severe allergic reaction that affects multiple body systems, such as the skin, respiratory system, gastrointestinal tract, and cardiovascular system. It is a life-threatening condition that requires immediate medical intervention, as it can lead to shock, airway constriction, and a rapid drop in blood pressure. Symptoms of anaphylaxis can include difficulty breathing, swelling of the throat, a rash, and potentially loss of consciousness. This severe reaction often occurs after exposure to an allergen, such as certain foods, medications, or insect stings.

The other options do not accurately describe this severe allergic reaction. Shock is a condition characterized by inadequate blood flow to the organs, which can occur during anaphylaxis but is not synonymous with it. "Sign" refers to an observable indication of a condition, while "symptom" pertains to the experiences of the patient, such as discomfort or pain. Neither "sign" nor "symptom" encapsulates the systemic nature and severity of anaphylaxis.