H18 Scabies: can we repurpose treatments from the past?

Abstract The UK is currently in the grip of a scabies epidemic. Current treatments seem to be either unavailable or ineffective, with multiple cases of permethrin resistance being reported. The British Association of Dermatologists has highlighted the shortage of scabies treatments and the lack of national tracking of cases. Scabies is not new, so can we learn from experiences and treatments of the past to help us in the present and the future? Scabies has irritated mankind for hundreds of thousands of years. The first treatments were based on sulfur and have been used for at least 5000 years. Sulfur is an irritant; it is unpleasant to use but can be effective. Lindane, created in 1825 but not used commercially until the 20th century is rarely used now due to its neurotoxicity and possible carcinogenic nature. It is still available but is banned in many countries. More treatments became available in the early 20th century due to the explosion of scabies cases associated with World War I. Benzyl benzoate, balsam of Peru and beta-naphthol were all successfully used to treat thousands of afflicted infantrymen. All have their limitations: benzyl benzoate and balsam of Peru commonly cause allergic reactions, and beta-naphthol may cause death. A reformulation of benzyl benzoate may be possible (its cure rate is a remarkable 86%), but overuse can lead to neurotoxicity. Dermatologists in World War II experimented with their own recipes. John Ingram reported in 1942 that a benzyl benzoate lotion of ‘equal parts soft soap and spirit’ gave ‘excellent results and caused no skin irritation’. New uses of old medicines may be one way forward. Tea tree oil has scabicide properties and is undergoing investigations for possible topical use. Oral ivermectin (discovered in 1975), although currently not licensed for scabies in humans, will probably be used in thousands of patients if the current surge of cases continues. There is the possibility that the topical form of ivermectin could be equally effective, and further studies are needed. Better formulation of old drugs may be possible to make them less irritant and cause fewer allergic reactions. Our current reliance on a tiny range of ‘safe’ topical therapies for treating scabies is clearly not working as the incidence of cases continues to rise. While work on developing new treatments and ways of dealing with this timeless problem continue, we also need to explore old treatments and reformulate irritant therapies.