The fertilized, female mite tunnels into the superficial skin layer (stratum corneum), forming burrows in which she lays her eggs and deposits feces (scybala).
After 2 months, the female parasite dies on site.
Following a period of 3 weeks, the larvae mature into adult mites, maintaining the infestation cycle.
The excretions of the mites and their decomposing bodies contain antigens which cause an immunological response (see type IV hypersensitivity reaction), presenting as severe pruritus and excoriations.
Clinical features
Intense pruritus that increases at night
The name “scabies” comes from “scratch”
A warm bed or bath intensifies the pruritus because the mite becomes more active.
Skin lesions
Burrows of 2–10 mm in length
Predilection sites
Wrists (flexor surface)
Medial aspect of fingers
Interdigital folds (hands and feet)
Male genitalia (e.g., scrotum, penis)
All other intertriginous areas of the skin (anterior axillary fold, buttocks)
Diagnostics
Detection of mites, larvae, ova, or mite feces
Revealed in dermoscopy
Microscopic examination of the skin
Skin scraping and histology
Treatment
Drug of choice: permethrin 5% lotion
Alternatives
Oral ivermectin: especially indicated in large outbreaks or severe forms of scabies
