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

<b><i>Background:</i></b> 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 <i>Demodex</i>, a microscopic commensal organism that resides in or near hair follicles and sebaceous glands. Although <i>Demodex</i> 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 <i>Demodex</i> in rosacea is currently lacking. <b><i>Summary:</i></b> As circumstantial evidence, non-invasive skin-detecting techniques have shown abnormally elevated numbers of <i>Demodex</i> in rosacea patients. Increased cytokine levels such as IL-10, IL-8, and IL-12p70 have been observed in human sebocytes following the <i>Demodex</i> challenge, and acaricides have been found to be effective in rosacea therapy, all point to a close relationship between <i>Demodex</i> 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 <i>Demodex</i>-associated rosacea, with the ultimate goal of improving patient outcomes.