Which of the following is NOT a symptom of anaphylaxis?

The correct answer is persistent headache, which is typically not associated with anaphylaxis. Anaphylaxis is a severe, life-threatening allergic reaction that presents with a rapid onset of multiple symptoms, primarily affecting the respiratory and cardiovascular systems. Common symptoms of anaphylaxis include dizziness, which may occur due to hypotension or decreased blood flow to the brain; wheezing, resulting from airway constriction; and cyanosis, which indicates inadequate oxygenation of the blood and is a critical sign of respiratory distress.

Persistent headache, while it can be a symptom of various other medical conditions, is not a direct symptom of anaphylaxis. During an anaphylactic reaction, the body's immediate response focuses more on airway obstruction and circulatory failure rather than causing headaches, which may occur due to other factors like dehydration or stress but are not characteristic of anaphylactic shock itself. Understanding the key symptoms of anaphylaxis is essential for prompt recognition and treatment, which can be life-saving.