Demodex mites colonize the pilosebaceous units of persons with normal skin without inducing inflammation. Increased Demodex mite density is seen in patients with rosacea and their potential to trigger inflammation has been suggested. Topical Ivermectin is effective in clearing inflammatory lesions of rosacea, possibly by anti Demodex activity. We postulated that in certain biological circumstances (normal skin) mites downregulate the inflammatory response, while in disordered circumstances (rosacea) they upregulated it. We studied the effects of Demodex mites (live and ruptured) on the production of inflammatory mediators by two primary cell types. Demodex mites were extracted from control subjects. Mites were ruptured to release internal contents or were maintained viable intact in culture medium. Rat preputial sebocytes (RPS) and human peripheral blood mononuclear cells (PBMCs) were challenged with live and ruptured mites. The secretion of inflammatory cytokines and chemokines was assessed using multiplex MSD assays and/or proteome profiler array analysis. In RPS cell cultures IL-6 secretion was down regulated by both intact live and ruptured control mites while GRO production was upregulated threefold in the presence of ruptured mites. Array analysis identified downregulation of MIP-3 α, CINC-4, IL-1ra, LIX, Thymus Chemokine and VEGF in response to ruptured mites. PBMC cultures exposed to both live and ruptured control mites showed significantly increased TNF-α production. These results indicate a potential for Demodex mites to influence the cellular inflammatory response in vitro. The predominant effect in sebocytes is downregulation (as expected from the presence of mites in normal subjects without inflammation). However, ruptured mites (as may be increased in rosacea) have the capacity to stimulate GRO production and attract neutrophils. In normal circumstances mites are not exposed to PBMCs. Compromised or ruptured follicles may expose mites that then have the capacity to induce TNF-α production by these cells leading to significant inflammation.