The nurse is assisting in the administration of IV vancomycin to a client who has methicillin-resistant Staphylococcus aureus (MRSA). Which of the following findings indicate an allergic reaction to the medication?

Rationale: A. Hypertension: Hypertension is not typically associated with an allergic reaction to vancomycin. Hypotension may occur in severe reactions like "red man syndrome," but elevated blood pressure is generally unrelated to allergic responses. B. Headache: Headache is a possible side effect of many medications, including vancomycin, but it does not specifically indicate an allergic reaction. It is a nonspecific symptom and usually does not warrant discontinuation unless severe. C. Tinnitus: Tinnitus is a sign of ototoxicity, a known adverse effect of vancomycin, especially with high doses or prolonged use. However, it is not indicative of an allergic reaction but rather toxicity affecting the auditory system. D. Urticaria: Urticaria, or hives, is a classic manifestation of an allergic reaction involving histamine release causing itchy, raised, red skin lesions. Its presence during vancomycin administration signals hypersensitivity and requires immediate attention.