Purpose: To perform a comprehensive, multifactorial analysis of potential risk factors (demographic and clinical) for contact allergy to neomycin sulfate, a common adverse reaction resulting from the topical use of this drug; especially in some subgroups of the population.
Methods: Retrospective analysis of allergy test data of the Information Network of Departments of Dermatology (IVDK, www.ivdk.org) between 1998 and 2003, including all patients patch tested with a standard screening series because of suspected allergic contact dermatitis (ACD). As one outcome, a positive (allergic) test reaction to neomycin sulfate was considered. An alternative outcome included only those patients with a positive test to neomycin sulfate and a final diagnosis of ACD. The association between outcome and potential risk factors was analyzed with Poisson regression analysis, deriving prevalence ratios (PR) as risk estimates.
Results: Of the 47,559 patients tested, 2.5% had positive reactions to neomycin sulfate, while in 1.1% ACD was additionally diagnosed. The results of the multifactorial analysis indicated that the risk of both outcomes decreased slightly during the period covered; was higher among patients with leg dermatitis; varied significantly with age and increased progressively with the number of additional positive reactions to other standard series allergens. Cross-reactivity to other, selectively tested, aminoglycoside antibiotics was substantial (kappa = 0.67; 95%CI: 0.63-0.71) for framycetin sulfate, to low (kappa = 0.33; 95%CI: 0.27-0.37) for gentamicin sulfate.
Conclusions: The prevalence of contact sensitization to neomycin sulfate was noteworthy among patients patch tested in the IVDK centers. Supplementing clinical epidemiology, neomycin contact allergy has been estimated to be relatively common even on the level of the unselected population (prevalence approx. 1%). Hence, the topical use of neomycin sulfate by patients should be carefully monitored, considering its potential to induce ACD, with emphasis on subgroups at risk.