Comment

Generally, it is believed that all mites and their eggs are killed soon after treatment. Confirmation of cure is therefore difficult because mites may not be detectable in post-treatment skin scrapings. It is therefore impossible to determine success until sufficient time has passed to permit the various lesions resulting from the infestation to heal. Many people show considerable improvement after 14 days but a definitive clinical cure cannot be concluded until about 28 days after treatment, when all lesions present at the time of treatment should either be healed or resolving, without new lesions developing.

Three of the RCTs were conducted in developing countries. The fourth study was divided between the USA and Mexico.11 It is not known whether scabies mites may be more susceptible to treatment in communities where treatments are not generally available but it is likely that prior exposure to acaricidal chemicals may select for reduced sensitivity in mites in developed countries, and some cases of suspected resistance, particularly to lindane, have been recorded.27,29

Lindane products are still used against scabies in most western countries, despite its relative toxicity. In the UK the only lindane product was withdrawn on commercial grounds. The former market-leading product in the USA is now no longer produced for the same reason.

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