Contact allergy to benzalkonium chloride in patients using a steroid nasal spray: A report of 3 cases.

Benzalkonium chloride (BAC) is a bactericidal preservative excipient commonly found in steroid nasal sprays used to treat allergic rhinitis and nasal polyposis. In rare cases, BAC can be responsible for type I and type IV hypersensitivity reactions that can manifest as rhinorrhea, which a clinician might misinterpret as a lack of response to nasal spray therapy rather than a complication of it. We report 3 cases of type IV hypersensitivity reactions in patients who were being treated with mometasone nasal spray. We describe the epidemiology, clinical features, diagnosis, and treatment of these reactions.