Trombiculiasis

Trombiculiasis is a dermatitis caused by infestation with the larval stage of trombiculid mites, commonly known as chiggers, in the family Trombiculidae. In humans, the larvae attach to the skin and inject saliva that digests tissue; they feed on the resulting fluid. The mites do not burrow into the skin, but the resulting inflammatory and allergic reaction produces itching and skin lesions.

The condition is associated with outdoor exposure in warm, humid environments such as grassy or brushy areas, forests, and fields. It can affect hikers, outdoor workers, and people who spend time in vegetation-rich settings. Lesions typically appear at sites where clothing tightens or where skin is exposed, such as the ankles, waistline, groin, or axilla.

Clinical features include intensely pruritic papules or vesicles, often with surrounding redness and excoriation from scratching. The eruption usually develops within hours to a few days after exposure. Secondary bacterial infection can occur with scratching.

Diagnosis is usually clinical, based on the history of exposure and characteristic skin lesions. Other insect bites or dermatitis may be considered in the differential diagnosis.

Management focuses on symptom relief and preventing secondary infection. Treatments include washing the area, applying topical corticosteroids, and using oral antihistamines or calamine lotion to reduce itching. Infected wounds may require antiseptics or antibiotics. Severe, widespread itching may warrant a short course of systemic steroids in rare cases.

Prevention involves avoiding known risk areas, wearing protective clothing and tucking pants into socks, using insect repellents containing DEET, and applying permethrin to clothing. Showering after outdoor activity can help remove unattached mites.