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

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.

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.

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.

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.