D emodex folliculorum: its association with oily skin surface rather than rosacea lesions

BACKGROUND: Despite the predilection of Demodex folliculorum (DF) for human sebum, observational studies addressing a relationship between this agent and rosacea paid no attention to the effect of a potentially acting confounder, the oily nature of the skin. OBJECTIVES: To analyze whether a relationship exists between the presence of the mite in rosacea and oily cutis. MATERIALS AND METHODS: An observational study on 63 rosacea cases and 61 healthy controls, both discriminated according to their predominance of oily or dry cutis, was carried out to investigate demodectic density by the skin surface biopsy. RESULTS: While comparisons on the density of DF revealed no differences between patients and controls (Mann-Whitney U-test, P = 0.35), persons with an oily cutis had increased amounts of this mite on the skin surface (Mann-Whitney U-test, P < 0.05), irrespective of whether they had rosacea or not. CONCLUSIONS: The association between DF and oily skin rather than rosacea lesions gives no support for this agent being implied in disease pathogenesis.