Human scabies is caused by an Infestation of the skin by the human itch mite (Sarcopetes scabiei var. hominis). The adult female mite holds onto the skin with sucker-like appendages until it finds a suitable location. It then burrows into the upper layer of the skin laying eggs in the process. The female mite remains there and continues to lengthen her burrow and lay eggs for the rest of her life (1-2 months). Humans are the source of infestation as animals do not spread human scabies. 

Scabies is a common condition found worldwide and affects people of all races and all social classes. Scabies is spread by person-to-person, skin-to-skin contact and through articles such as bedding and clothing. Scabies can spread easily under crowded conditions where close body and skin contact is common. Institutions such as nursing homes, extended care facilities, prisons, and child care facilities are common sites of scabies infestations.

Scabies can be passed effortlessly by an infested person to his or her household members and sexual partners. Scabies in adults is frequently sexually acquired.

When a person acquires scabies for the first time, symptoms may not appear for up to 2 months. However, an infested person can transmit scabies even if they have no symptoms, until they are successfully treated and the mites and eggs are destroyed.

Itching, especially at night, is the earliest and most common symptom of scabies. In addition, a pimple-like itchy rash (scabies rash) is also common. These are caused by an allergic type reaction to the proteins and feces of the parasitic mite.

Tiny burrows, caused by the mite tunneling beneath the surface of the skin, may be seen. They appear as tiny raised and crooked lines on the skin surface and my be grayish-white or skin-colored.

The scabies rash or burrows are most commonly noted:

• Between the fingers
• On the wrist
• Elbow and armpits
• Waist
• Buttocks
• Shoulder Blades
• Nipples and penis

Diagnosis of a scabies infestation is usually made based upon the appearance and distribution of the rash and linear burrows.

It is recommended that, whenever possible, a scabies diagnosis should be confirmed from an identification of the mite, mite eggs, or mite fecal matter (scybala). this is done by removing the mite from its burrow with the tip of a needle or by obtaining a skin scraping. The material is then examined under a microscope to observe for mites, eggs, or fecal matter. If none of this material is found a person can still be infested with scabies as fewer then 10-15 mites may be present on an otherwise healthy person.

Medications used to treat and kill human scabies are called scabicides. They are available only with a doctor's prescription. There are no over-the-counter products tested and approved to treat human scabies. Always follow the manufacturer's instruction in the box or printed on the label.

Scabicide lotion or cream should be applied to all areas of the body from the neck down to the feet and toes. When treating infants and young children the medication should be applied to their entire head and neck as scabies can affect their face and scalp. Leave the lotion on for the recommended period of time before washing it off. Don clean clothing after treatment.

In addition to the infested person, treatment is also recommended for all household members, sexual contacts, and others who have had direct skin to skin contact with the infested individual. These people should be treated at the same time to avoid reinfestation.

Bedding. clothing, and towels used by the infested person, their household, sexual conducts, or others during a three day prior prior to treatment should be decontaminated. This is done by hot water washing and drying in a hot dryer, or by dry-cleaning. Because scabies mites do not survive more than 2 to 3 days away from human skin, the articles can also be sealed in a plastic bag for a period of 72 hours. 

Because the symptoms of scabies are caused by a hypersensitivity reaction to the mites, eggs, and feces, itching may continue for several weeks after treatment even if all the mites and eggs are killed. If 2 to 4 weeks after treatment itching is still present or if new burrows, rashes, or lesions appear, retreatment will be necessary.     


Last Reviewed: 05-18-11