What is Scabies
Scabies is a skin condition caused by mites living in your skin. Scabies, are named the human itch mite and are the most common cause of itching dermatosis. The itching and rash seen with a scabies infection result from burrowing of the skin by a mite and development of subsequent hypersensitivity reaction. The initial infestation can remain asymptomatic for up to 4-6 weeks while a reinfestation will elicit an immediate sensitization reaction and pruritus.
Transmission of Scabies
Transmission occurs primarily by intimate interaction (i.e. crowding, multiple sexual partners). Without host contact, the mites die within a day and transmission via contaminated bedding or clothing is rare. Host immunity and scratching at the site of infection serve to limit most infestations (<15 mites/person). Hyperinfestation (1000+ mites/person), also termed crusted scabies or Norwegian scabies, may occur in patients with glucocorticoid use, with immunodeficiency, or with a neurologic illness which limits scratching.
Treatment of Scabies
- Scabies treatment requires specific medication, which you can get either over the counter or prescribed by a doctor. You generally apply a cream or lotion based drug all over your body from the neck down and leave it on for at least eight hours. Treatment of a scabies infection may include use of both a scabicidal agent and an antipruritic. Scabicides are applied and massaged onto skin of the entire body from the neck to the toes and are washed off after eight hours with soap and water. Permethrin may be less toxic than lindane and are effective against lindane-resistant infestations.
- Treatment of crusted scabies requires use of a keratolytic agent such as 6% salicylic acid and a scabicidal agent. Successfully treated scabies infections are noninfectious within a day but the itching and rash may persist for weeks to months. Re-treatment with topical agents is often unnecessary and may worsen pruritus and contact dermatitis. Antihistamines, salicylates, and calamine lotion may be used to reduce pruritus. Topical glucocorticoids should only be used after successful treatment of the infection for lingering itching.
Scabicides or Medications for Scabies
Products used to treat scabies are called scabicides because they kill scabies mites; some also kill mite eggs. Scabicides used to treat human scabies are available only with a doctor’s prescription. No “over-the-counter” (non-prescription) products have been tested and approved to treat scabies.
- Permethrin Cream 5%. Permethrin is approved by the US Food and Drug Administration (FDA) for the treatment of scabies in persons who are at least 2 months of age. Permethrin is a synthetic pyrethroid similar to naturally occurring pyrethrins which are extracts from the chrysanthemum flower. Permethrin is safe and effective when used as directed. Permethrin kills the scabies mite and eggs. Permethrin is the drug of choice for the treatment of scabies. Two (or more) applications, each about a week apart, may be necessary to eliminate all mites. Children aged 2 months or older can be treated with permethrin.
- Crotamiton lotion 10% and Crotamiton cream 10%. Crotamiton is approved by the US Food and Drug Administration (FDA) for the treatment of scabies in adults; it is considered safe when used as directed. Crotamiton is not FDA-approved for use in children.
- Sulfur (5%-10%) Ointment. Sulfur in an ointment base (petrolatum) is safe for topical use in children, including infants under 2 months of age. The odor and cosmetic quality may make it unpleasant to use.
- Ivermectin. Ivermectin is an oral antiparasitic agent approved for the treatment of worm infestations. Evidence suggests that oral ivermectin may be a safe and effective treatment for scabies; however, ivermectin is not FDA-approved for this use. Oral ivermectin should be considered for patients who have failed treatment with or who cannot tolerate FDA-approved topical medications.