Evidence for the Clinical Association between <i>Demodex</i> and Rosacea: A Review

Abstract

Background: Rosacea is a chronic inflammatory dermatological condition in humans, and its pathogenesis remains unclear. However, the development of rosacea is suspected to be related to Demodex, a microscopic commensal organism that resides in or near hair follicles and sebaceous glands. Although Demodex is known to be a host-specific, obligate commensal organism, it is currently difficult to be cultured in vitro to parasitize and infect other animal hosts. Therefore, direct evidence for a pathogenic role of Demodex in rosacea is currently lacking. Summary: As circumstantial evidence, non-invasive skin-detecting techniques have shown abnormally elevated numbers of Demodex in rosacea patients. Increased cytokine levels such as IL-10, IL-8, and IL-12p70 have been observed in human sebocytes following Demodex challenge, and acaricides have been found to be effective in rosacea therapy, all point to a close relationship between Demodex and rosacea. Based on these findings, we conducted a comprehensive literature review to summarize the current state of knowledge, research insights, and clinical treatment recommendations for Demodex-associated rosacea, with the ultimate goal of improving patient outcomes. Key Messages: Rosacea appears to have a close bond with Demodex. Recent studies have implicated that Demodex mites are involved in the development of rosacea. Based on a comprehensive review of the current literature, we have cited substantial evidence supporting this relationship, proposed a possible vicious cycle between Demodex and rosacea, and illustrated the changes in immune responses during this process. In addition, we recommend that patients with both rosacea and Demodex infection be treated early with a combination of topical ivermectin and topical Th1 inhibitors to improve treatment outcomes.