Demodicosis

Demodicosis is a skin condition caused by overgrowth of Demodex mites, most commonly Demodex folliculorum and Demodex brevis. These microscopic mites are normal inhabitants of human hair follicles and sebaceous glands, especially on the face, but disease results when their numbers become excessive or the host’s immune response is altered. Demodex can also affect other mammals, most notably dogs, where Demodex canis causes demodectic mange.

In humans, demodicosis can present with facial redness, inflammatory papules and pustules, and itching. It is often associated with blepharitis when eyelids are involved. The condition may resemble rosacea and is more common in older adults, people with immunosuppression, hormonal changes, or stressful conditions that alter skin immunity. In horses and other animals, clinical signs include localized or generalized alopecia, erythema, scaling, and secondary infections.

Diagnosis relies on clinical suspicion supported by mite detection. Methods include skin scrapings or standardized skin surface biopsies, which reveal mites within hair follicles or sebaceous glands. Trichoscopy and eyelid sampling may aid in ocular involvement. Counting mites can help distinguish incidental presence from overgrowth, with higher densities and concordant symptoms supporting demodicosis.

Treatment focuses on reducing mite burden and addressing underlying factors. Therapeutic options in humans include topical or oral acaricides such as ivermectin-containing preparations and topical metronidazole, often combined with improved skin hygiene and treatment of blepharitis. In animals, management may involve specific antiparasitic agents and addressing immune status. Prognosis is favorable in immunocompetent individuals, though relapses can occur with ongoing risk factors.