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Family: Demodicidae

Demodex (follicle mites)

These extremely small mites, 0.1–0.4 mm long (Figure IV.3), have a worm-like transversely striated body with four pairs of stubby legs anteriorly. They infest a wide variety of mammalian hosts but are highly host-specific. More than one species may occur on the same host but in different tissues. For example, D. folliculorum lives in the hair follicles of humans and the stubby D. brevis is found in the sebaceous glands. The entire life cycle occurs in the follicles. In humans, infestations occur mainly in the region of the eyelids, nose and facial area. Infestations are usually higher in aged persons, in whom they may reach 100%. Diagnosis is by expressing sebum and examining it for mites. Infestations are usually benign, but dry erythema with follicular scaling, particularly in the region of the eyelids, may give rise to blepharitis. In the facial area there may be granulomatous acne. Gammexane (gamma benzene hexachloride) 0.5% in vanishing cream …