TLR2 and rosacea: However, high densities of D. folliculorum mites stimulate upregulation of TLR2 and induce secretion of inflammatory mediators by sebocytes.30,32 The chitin exoskeleton of the mites also increases TLR2 activity.17 In a cross-sectional prospective study comparing rosacea patients with sex- and age-matched controls, the skin of rosacea patients had over a 5-fold increase in D. folliculorum density and increased expression of pro-inflammatory cytokines such as IL-8 and TNF-α.33