For which condition is Permethrin (Elimite) the preferred treatment when applied overnight from the neck down?

Permethrin, commonly known under the brand name Elimite, is a topical insecticide that is specifically approved for the treatment of scabies, a skin condition caused by infestation with the Sarcoptes scabiei mite. The preferred method of application involves applying it all over the body from the neck down and leaving it on overnight to effectively kill the mites and their eggs.

Scabies is characterized by intense itching and a rash, and it often requires a treatment that can penetrate the skin where the mites burrow. Permethrin works by disrupting the nervous system of the mites, leading to their eventual death.

In contrast, eczema, herpes simplex, and psoriasis are different dermatological conditions that do not respond to permethrin. Eczema is more appropriately managed with topical corticosteroids or moisturizers, herpes simplex is treated with antiviral medications, and psoriasis is typically managed with a range of therapies, including topical agents, phototherapy, or systemic medications rather than insecticides. Thus, the use of permethrin is specifically indicated for scabies, making it the correct choice in this scenario.