Demodex and rosacea: Is there a relationship?

Purpose: The objective of the study is to compare the frequency of Demodex on the eyelash follicle of patients with rosacea and referents without rosacea or ophthalmological disorders. Methods: This is a comparative, open, observational, and cross-sectional study that included 41 patients diagnosed with rosacea and 41 referents without rosacea diagnosis or ophthalmic alterations. The individuals underwent a slit-lamp examination in which two eyelashes per eyelid were removed with fine forceps. The presence of Demodex was sought by direct visualization under a light microscope. The results were expressed as "positive" when at least one mite on one lash was found and "negative" when no mite was identified. Chi-square test was used to compare the presence of mites in both groups. Results: Eighty-two study individuals (45 females and 37 males) were included, of which 41 patients were diagnosed with rosacea and 41 were without rosacea or ophthalmic alterations. The average mean age was 37 years with a minimum of 19 and a maximum of 87 years. Of the 41 patients with rosacea, 31 had erythematotelangiectatic rosacea and 10 had papulopustular rosacea. There were no patients with phymatous or ocular rosacea. The presence of Demodex was found in 32 patients: 24 patients with rosacea diagnosis (16 of the erythematotelangiectatic subtype and 8 of papulopustular subtype) and 8 patients without rosacea or ophthalmic alterations (P <= 0.001). Conclusion: Rosacea was found to be a statistically significant risk factor for Demodex infestation in eyelashes, irrespective of age and sex, with a higher prevalence in papulopustular variety.