摘要

Objectives: To highlight benzyl alcohol hypersensitivity as a rare but relevant complication of BoNT-A procedures. Introduction: Botulinum toxin type A (BoNT-A) is widely used in aesthetic and therapeutic medicine. Although the FDA recommends preservative-free saline for reconstitution, many clinicians use bacteriostatic saline containing benzyl alcohol to reduce injection discomfort. Benzyl alcohol, however, is a known allergen capable of triggering immediate hypersensitivity reactions. Awareness of this potential risk is crucial for safe and individualized BoNT-A practice. Materials / method: A 37-year-old woman developed facial urticaria and angioedema shortly after onabotulinumtoxinA injections reconstituted with bacteriostatic saline containing benzyl alcohol. A reproducible reaction occurred following a 0.05 mL intradermal test dose, confirming hypersensitivity. Negative patch and prick tests were considered false negatives due to insufficient allergen concentration and limited dermal penetration. Results: Following the intradermal test, identical urticarial plaques and angioedema developed within 15 minutes, confirming immediate hypersensitivity to benzyl alcohol rather than to botulinum toxin itself. Symptoms resolved completely within 72 hours after a short course of systemic corticosteroids. No further reactions occurred when reconstituted with preservative-free saline. Conclusion: Bacteriostatic saline, though commonly used for BoNT-A reconstitution, may provoke immediate hypersensitivity due to benzyl alcohol. Even with negative patch tests, clinicians should suspect this diluent in cases of post-injection urticaria or angioedema. Switching to preservative-free saline is recommended to prevent recurrence and ensure patient safety.