Scabies Treatment Failure: Beyond Drug Resistance and Toward a Multidimensional Understanding

Scabies, caused by Sarcoptes scabiei var. hominis, remains a major global health problem affecting both resource-poor and high-income regions. Despite the availability of effective treatments, treatment failure continues to pose a challenge to disease control and has become an increasingly recognized clinical and public-health concern. However, treatment failure is often attributed solely to drug resistance, overlooking the complex interplay of biological, clinical, behavioral, and environmental factors. This narrative review summarizes the current state of knowledge regarding the multifactorial causes of scabies treatment failure. Key areas include true parasitological failure, pharmacological limitations, and emerging resistance; pseudoresistance resulting from incorrect treatment administration; reinfestation from untreated contacts; environmental transmission; diagnostic uncertainties; and host-related inflammatory reactions such as postscabies pruritus. The review also proposes a multidimensional conceptual framework to distinguish true treatment failure from apparent clinical failure and to explain how interacting factors contribute to unsuccessful treatment outcomes. Identifying these determinants is crucial for optimizing treatment strategies, improving treatment success, and guiding future research aimed at combating scabies.