Contact hypersensitivity and Demodex mite infestation in patients with rosacea: a retrospective cohort analysis

ABSTRACT

Background: Contact hypersensitivity or Demodex mite infestation is commonly reported in patients with rosacea. However, the associations and clinical implications of these two phenomena are poorly described in the literature. Objectives: This study aimed to investigate the association between clinical characteristics, contact sensitization profiles, and Demodex mite infestation in patients with rosacea. Materials & Methods: We retrospectively reviewed 189 patients diagnosed with rosacea, and categorized the patients into a rosacea-contact hypersensitivity or rosacea-non-contact hypersensitivity group. Results: The rosaceacontact hypersensitivity group had older age (median 45.5 vs. 37.0 years; p = 0.006), a higher frequency of itching (63.0% vs. 45.1%; p = 0.040), and a higher Demodex mite density (15.0/cm2 vs. 7.0/cm2; p = 0.002) than the rosacea-non-contact hypersensitivity group. Nickel sensitization was correlated with a higher Demodex mite density, female sex, and papulopustular subtype of rosacea. Based on the multivariate regression model, a favourable clinical outcome was correlated with nickel sensitization alone (odds ratio 2.20, 95% confidence interval 1.01-4.81). Conclusion: Patients with rosacea and contact hypersensitivity showed distinctive clinical features and a higher Demodex mite density. The association between nickel sensitization, Demodex mite infestation, and treatment response may reflect the role of allergen-specific TH polarization in the pathogenesis of rosacea.