Twist in a Long-Standing Glaucoma Treatment Journey: Delayed Hypersensitivity to Benzalkonium Chloride

Abstract A 79-year-old male with a long-standing history of pseudoexfoliative glaucoma presented with persistent periocular eczema, itching and eyelid swelling. Despite multiple consultations and empirical treatments for presumed allergic conjunctivitis and dermatological conditions, his symptoms persisted. The intraocular pressure remained well controlled, and there were no signs of intraocular inflammation or glaucomatous progression. After ruling out common allergens and other causes, a trial switch from a benzalkonium chloride (BAK)-preserved anti-glaucoma medication to a preservative-free formulation resulted in complete symptom resolution. This case emphasizes the importance of considering preservative toxicity, even after years of well-tolerated use, and the need for a high index of suspicion for delayed hypersensitivity reactions.