Demodex folliculorum and Demodex brevis in cutaneous biopsies.

The hair follicle mites Demodex folliculorum and Demodex brevis are ubiquitous obligatory ectoparasites of man. We studied these mites in a consecutive series of skin biopsies submitted to a dermatopathology laboratory; 10% of all biopsies and 12% of all follicles contained demodectic mites. The prevalence of both species increased with age, but D. brevis had a lower prevalence. The face was most heavily infested by both species, but D. brevis had a wider distribution on the body. Males were more heavily infested than females with both species, the difference being strongest for D. brevis. Other ecologic characteristics noted include the type of follicles infested, follicular dilation, perifollicular inflammation, and the presence of a dense homogeneous eosinophilic material surrounding the mites. These data confirm ecologic and epidemiologic differences between the two species and emphasize that they should be distinguished in future studies of the roles these mites may play in a variety of disease states.