Which factors influence Demodex proliferation? A retrospective pilot study highlighting a possible role of subtle immune variations and sebaceous gland status

Demodex folliculorum and brevis are commensal mites that live in low densities human pilosebaceous follicles as part of the normal adult microbiota, but give rise to demodicosis and, possibly, rosacea, when they proliferate excessively. This proliferation is favored by various factors, including age, marked immunosuppression, sebaceous gland hyperplasia, hypervascularization-related factors. To study possible factors influencing mite proliferation, we explored effects different variables on (Dd) a retrospective two groups subjects selected basis their clinical diagnosis: Demodex+, consisting with or centro-facial papulopustules suggesting rosacea (n = 844, mean Dd 263.5 ± 8.9 D/cm2), Demodex?, other facial dermatoses healthy skin 200, 2.3 0.4 D/cm2). were measured using consecutive standardized surface biopsies (SSSB1 [superficial] SSSB2 [deep]) taken from same site each subject. In Demodex+ group: SSSB1 decreased age women (p 0.004), increased men 0.001) (the pattern was similar for + 2, not statistically significant); Dds lower those who had received cortisone (either topically systemically); 13 (1.5%) known 62 (7.3%) hypothyroidism, 20 (3.6% women) there reported link pregnancy; 78 (9.2%) pair family household; associated bacterial infection suspected, Staphylococcus epidermidis often isolated. Our results suggest close interactions between mite, size function, subtle variations immune status. Potential should be further investigated, pregnancy, corticosteroid administration, epidermidis, contagiousity, genetic background.