A nurse is evaluating a client's response after initiating an intermittent IV bolus of vancomycin. Which of the following findings indicates the client is experiencing an allergic reaction to the medication?

A. Hypertension: An allergic reaction to vancomycin typically does not cause high blood pressure. Blood pressure changes may occur with severe reactions, but hypertension is not a primary indicator. B. Dyspnea: Difficulty breathing indicates a hypersensitivity or allergic reaction to vancomycin. Respiratory distress, along with potential hypotension, rash, or urticaria, signals the need for immediate intervention. C. Tetany: Tetany is related to hypocalcemia or electrolyte imbalances, not vancomycin allergy. It is not an expected manifestation of an allergic response. D. Headache: Headache is a nonspecific symptom and is not characteristic of an allergic reaction to vancomycin. It does not reliably indicate hypersensitivity.