How to determine if a facial rash is caused by a subcutaneous mite? - briefly
«Examine the lesion with dermoscopy for characteristic burrows or motile particles, then obtain skin scrapings or a punch biopsy for microscopic identification of mite bodies or eggs». Confirmation of mites establishes the rash as mite‑induced; absence directs evaluation toward other causes.
How to determine if a facial rash is caused by a subcutaneous mite? - in detail
Assessing a facial eruption for possible mite involvement requires systematic evaluation. Begin with a thorough patient history that records onset, progression, associated itching, exposure to infested environments, and any previous dermatological diagnoses. Note any recent travel, contact with animals, or use of topical cosmetics that may harbor organisms.
Physical examination focuses on lesion morphology. Look for papules, pustules, erythema, or scaling localized around hair follicles, particularly on the cheeks, nose, and forehead. Presence of “sacs de colle” (collapsed follicular openings) or “verrues” (wart‑like nodules) may suggest parasitic activity.
Dermoscopy or videodermatoscopy provides magnified visualization of the skin surface. Characteristic findings include moving translucent bodies within hair shafts, “demodex tails,” or burrows resembling fine linear tracks. Document any observed movement, as live mites confirm active infestation.
If dermoscopy is inconclusive, obtain skin samples. Perform a superficial skin scraping or plucking of affected hairs, place material on a glass slide with mineral oil, and examine under a microscope at 100–400× magnification. Identify mite morphology: elongated bodies with four pairs of legs for Demodex species, or oval bodies with ventral suckers for Sarcoptes scabiei. Count mites per field; a density exceeding 5 mites per cm² typically indicates pathogenic involvement.
When microscopic evaluation yields ambiguous results, proceed to a punch biopsy (3–4 mm) of an active lesion. Histopathology reveals follicular inflammation, presence of mite bodies, and associated eosinophilic infiltrates. Special stains (e.g., Giemsa) enhance visualization of cuticular structures.
Laboratory tests support differential diagnosis. Conduct complete blood count to detect eosinophilia, which may accompany parasitic skin disease. Serologic assays for specific mite antigens are available for scabies but not routinely for Demodex; however, positive IgE levels can corroborate an allergic component.
Differential diagnosis excludes common dermatologic conditions such as acne vulgaris, rosacea, seborrheic dermatitis, and allergic contact dermatitis. Compare lesion distribution, trigger factors, and response to standard therapies to narrow possibilities.
Treatment decisions depend on confirmed mite presence. For Demodex overgrowth, topical agents containing ivermectin, metronidazole, or benzoyl peroxide are effective. For scabies, apply permethrin 5 % cream to the entire body, including the face, and repeat after 7 days. Oral ivermectin (200 µg/kg) serves as an alternative for extensive or refractory cases.
Follow‑up evaluation after two weeks assesses therapeutic response. Resolution of lesions, reduction in mite count on repeat microscopy, and absence of new papules confirm successful management. Persistent symptoms warrant repeat biopsy or referral to a dermatologist for advanced diagnostics.