Which of the following is a sign of anaphylaxis?

Difficulty breathing is a hallmark sign of anaphylaxis, which is a severe and potentially life-threatening allergic reaction. In anaphylaxis, the immune system reacts excessively to a substance, leading to swelling, bronchoconstriction, and airway obstruction. This can manifest as wheezing, shortness of breath, or a tight feeling in the chest, all of which contribute to the characteristic difficulty in breathing.

Recognizing this symptom is critical for immediate action, as anaphylaxis can progress rapidly and requires prompt administration of epinephrine, among other interventions. The presence of respiratory distress is often accompanied by other symptoms such as swelling of the face or throat, hives, and gastrointestinal distress, but the difficulty in breathing is the most life-threatening and recognizable symptom that requires urgent medical intervention.