Purpose: Demodex folliculorum is a transparent mite, 0.3 - 0.4 mm long, which asymptomatically
parasitizes the human pilosebaceous follicles. D. folliculorum is observed in normal
skin with a prevalence of 100% and a density of ≤ 5 D/cm2 in the adult
population. Materials and Methods: This study evaluated the differences in pH on the five facial sites between the
two populations with and without D. folliculorum. The relationship between pH and skin surface oil was analyzed
in populations with and without Demodex mites. Mongolian 750 subjects (370
males and 380 females) aged 16 - 84 years, who
lived in Ulaanbaatar city, were enrolled in this study. The eligibility
criteria included a minimum age of 16 and no physical and dermatologic illness,
no cosmetic. Results: Skin surface
oil among the five facial areas differed significantly in both subjects with
and without Demodex folliculorum (P < 0.001). When the skin surface oil on the T-zone, U-zone was
compared, those on the T-zone were significantly higher than those of the
U-zone (P < 0.001) in
both populations (P< 0.01). The pH levels on the five facial sites, and
U-zone, T-zone and MFpH differed significantly in among both subjects with and
without Demodex folliculorum (P < 0.001). In both groups, the pH levels of the U-zone were
significantly lower than the pH of the T-zone (P < 0.001). Conclusions: Among the five facial sites in subjects with Demodex
folliculorum, there were significant negative correlations between skin surface
oil and pH on the forehead (p < 0.001, r = 652), cheek (P < 0.001, r = 0.656), nose (P < 0.001, r = 0.754), chin (P < 0.001, r = 0.679), and T-zone (P < 0.001, r = 0.698), MFSE-MFpH (P < 0.001, r = 0.483). In contrast, among the five
sites in subjects without Demodex folliculorum, a significant negative
correlation between skin surface oil and pH was observed on the forehead (p < 0.001, r = 766), cheek (P < 0.001, r = 0.798), nose (P < 0.001, r = 0.706), chin (P < 0.001, r = 0.823), and T-zone (P < 0.001, r = 0.602), U-zone (P < 0.001, r = -0.550)