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

Abstract

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. This study aimed to investigate the association between clinical characteristics, contact sensitization profiles, and Demodex mite infestation in patients with rosacea. We retrospectively reviewed 189 patients diagnosed with rosacea, and categorized the patients into a rosacea-contact hypersensitivity or rosacea-non-contact hypersensitivity group. 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/cm2vs. 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). 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.