What causes scabies?

Sarcoptes scabiei subspecies hominis is a mite that causes scabies.  It is less than 1 millimeter in size and therefore very difficult to see without a microscope.  The mite burrows under the skin, typically in a skin crease such as between the fingers, at the wrists, around the waistline, between the buttocks, in the armpit or belly button.  Here, the female mite travels through the skin 0.5 to 5 millimeters per day.  The mite leaves behind eggs and droppings that cause a red, itchy bump or red line on the skin.

But wait... can I get scabies from my dog?

Dog scabies is caused by a different subspecies of Sarcoptes scabiei (subspecies canis).  Humans who come in close contact with a dog or puppy with "mange" may be infected with dog scabies.  This infection causes similar symptoms as human scabies (small, itchy red bumps), but is much milder and resolves without treatment.  Transmission of scabies from dogs to humans is uncommon.

How is scabies spread?

Scabies is spread from person to person.  It can infect a person of any age, any nationality, rich or poor.  When one person is infected, everyone in the same household is at risk for developing the infection.  The scabies mite does not live long in the environment, therefore contaminated surfaces (i.e., beds, furniture, carpeting) are uncommon means of transmission.

What are the symptoms of a scabies infection?

A first-time infection usually produces symptoms 4 to 6 weeks after exposure.  If it is a repeat infection, symptoms typically occur more quickly (within 1-4 days) but are milder.

• Red or brown bumps on the skin (usually in a skin crease such as between the fingers, in the armpit or belly button, at the waist line, or around the wrist)
• Reddish lines on the skin, often twisty and less than 1 cm long
• Severe itching at the site of infection
• Scratching the bumps often leads to minor skin trauma (i.e., excoriation)
• Bacteria may cause a secondary infection with redness, tenderness and swelling at the infection sites

In infants, infection often occures in non-crease areas of the skin and may cause red bumps with blisters.

How is a scabies infection diagnosed?

A doctor may suspect scabies based on the appearance of the lesions.  Especially if they are found between the fingers, are extremely itchy and have the characteristic linear red tracks.

The lesions may be scraped with a small blade or microscope slide.  The scraped debris may be viewed under a microscope.  Either the mite, or the mites eggs or droppings may be identified.

How is scabies treated?

A lotion or cream containing a medicine called permethrin is often used.  This lotion is spread over the entire body and left in place for approximately 8 hours.  This may have to be repeated in a few weeks if the first application is not successful.

All family members and close contacts of the infected person should also be treated.

Scabies does not live in the environment for an extended period of time, however bedding and clothing that was contacted or worn within 4 days of starting treatment should be washed and hot dried in a clothes dryer.

There is no need for extensive cleaning or vacuuming of the house.

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