Application errors associated with topical treatment of scabies: an observational study.

Background: In recent years, there has been a significant increase in scabies infestations throughout German-speaking countries. Given the high frequency of treatment failures, the question arises as to whether topical permethrin treatment is always performed correctly.
Patients and Methods: Our department uses a fluorescent test cream to teach patients on how to correctly apply topical permethrin. In the context of a prospective observational study of 21 patients, we systematically assessed and analyzed potential application errors.
Results: None of the participants succeeded in adequately applying the cream to the entire skin as previously instructed. The median number of regions left untreated was six (minimum: 2; maximum: 18), which included a median body surface area of 6 % (minimum: 2 %; maximum: 30 %). With regard to predilection sites of scabies, the ankles were left untreated in 62 % of cases, followed by the interdigital spaces (toes) (33 %) and the sacral region (24 %). All patients considered the pretreatment training to be very useful.
Conclusions: The present findings clearly demonstrate potential shortcomings when it comes to the application of topical antiscabies treatment. This may provide a (potentially underestimated) explanation for the large number of reports on treatment failures in this regard, which falsely suggest potential treatment resistance.
(© 2020 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.)