What is a common complication following a severe allergic reaction?

A severe allergic reaction often leads to anaphylaxis, which is a life-threatening condition characterized by the rapid onset of symptoms affecting multiple organ systems. This can include difficulty breathing due to airway restriction, swelling of the throat, a drop in blood pressure, and potentially loss of consciousness. Anaphylaxis requires immediate intervention, typically through the administration of epinephrine, and can escalate quickly without proper treatment.

Other conditions, while they may have some association with allergies, do not represent a direct progression from the severe allergic reaction itself. For instance, hyperventilation may occur in response to anxiety or stress, an asthma attack can be related to allergy triggers but is not a direct result of the allergic reaction itself, and pneumonia is an infection that does not typically follow an allergic event. Therefore, anaphylaxis is the most appropriate answer as it represents the serious consequence of a severe allergic reaction, necessitating prompt emergency medical response.