Contact Allergy to Neomycin in Consecutively Patch Tested Danish Eczema Patients from 2000 to 2023: A Cross-Sectional Study.

Background: Neomycin is an aminoglycoside antibiotic that may cause contact allergy. It was withdrawn as a medicine for human use in Denmark in October 2009 but is still found in some vaccines. Objectives: To identify time trends in contact allergy to neomycin in the period from 2000 to 2023. Methods: A cross-section study of patients >= 18 years consecutively patch-tested with neomycin sulfate (20% in pet.) at Gentofte Hospital, Denmark, during the period 2000-2023 was conducted. Results: The overall prevalence of contact allergy to neomycin was 1.4%. The prevalence was significantly lower in the period '2010-2023' (1.2%) than in '2000-2009' (1.8%) (p < 0.005). Contact allergy to neomycin was significantly positively associated with facial dermatitis and age >40 years, and significantly negatively associated with occupational dermatitis and hand dermatitis. No changes in sex, occupational dermatitis, atopic dermatitis, hand dermatitis, leg dermatitis, facial dermatitis, or age > 40/<= 40 (the MOAHLFA-index) were identified when comparing neomycin contact allergic-patients in the two periods '2010-2023' and '2001-2009'. Conclusion: Neomycin is a rare cause of contact allergy in Denmark with a significantly lower prevalence following its withdrawal as a medicinal product for human use in Denmark in 2009.