This week's Clinical Therapeutics review in the New England Journal of Medicine discusses scabies, and in particular the place of permethrin and ivermectin in its treatment.

As usual in this series, the authors present a case vignette: this describes a familial group of cases in an Australian aboriginal population, discovered through presentation of a child of the family at a clinic with infected skin sores due to scabies. The suspected source is an elderly aunt living with the family who was found to have scabies hyperinfection (crusted scabies, Norwegian scabies), which occurs when the body is unable to mount an effective immune response to the infection.

The authors discuss the clinical aspects of scabies, and its treatment. Topical treatment is usually adequate and while a number of drugs may be used they describe the use of permethrin. In severe cases, systemic therapy with oral ivermectin is necessary. They note the evidence for scabies treatments, which is limited, and quote a Cochrane review on the subject. Ivermectin is less effective in single doses, as it does not sterilise eggs; however in two doses given at least a week apart, it can give cure rates of 95%.  Areas of uncertainty include increasing resistance to current treatments, and the safety of ivermectin at extremes of age.

Guidelines on scabies treatment have been produced by the US Centers for Disease Control, and the British Association of Sexual Health; the authors have produced a guideline on the management of crusted scabies.

Finally, they describe the therapy of the family presenting for the case vignette, noting that the case of crusted scabies is unusual: the aunt will require hospital admission for treatment and should be strictly isolated to prevent transmission to staff.