Scratching at the irritated skin often causes sores, which may become infected with bacteria. In incubation period from infestation to when symptoms will begin to appear is generally around four weeks, or up to six weeks, if the person has never been infected previously. People who have been infested with scabies before will have symptoms begin to appear much more rapidly, sometimes within a few hours of infestation. This is due to the increased sensitivity of the skin from previous infestations. People do not become immune to infestation after treatment. Diagnosis of scabies is most commonly made by an observation of the irritated skin and locating a scabies-like rash or skin burrows. The burrows are often difficult to see themselves, as they are only between five to fifteen millimeters long and about the width of a thread. There may be a blister at the end of the burrow, but not always. Doctors may chose to take a skin scraping to look for mites, mite eggs, or mite fecal matter in the skin to confirm the diagnosis, but this method is also not perfect. Often, test results will be returned negative for scabies even if the person is in fact infested because there are usually less than ten mites on the entire body of an infested person.

In many cases, by the time an infested person seeks medical treatment, the burrows have been scratched due to itching, and the burrows have been disrupted. Often by this time there is also a secondary infection of bacteria. People who shower frequently may be more difficult to diagnose. Additionally, if topical steroids have been used previously it may make the clinical symptoms harder to diagnose.

The scabies rash may become increasingly worse if not treated, especially if bacterial infection has occurred. People who have weakened immune systems and the elderly may contract a more...

In extreme untreated cases, Norwegian scabies can be fatal.
Anyone who is diagnosed with scabies should be treated. Anyone who has prolonged skin contact or sexual contact with that person should also be treated. Treatment should be done at the same time to prevent reinfestation. Generally, a five percent permethrin cream is used for treatment. The cream should be applied to clean skin, and the patient should try to keep the skin cool. The cream should be applied in a thin layer to all areas of skin below the neck. Having another person apply the cream is often recommended so that no area of the skin is missed.

The cream must be left on for at least eight hours, at which point it must be washed off thoroughly.

If the hands are washed during the eight hours of treatment, the cream should be reapplied to that area. The cream should not be left on the skin for more than twenty-four hours. A slightly more gentle treatment may be used for pregnant or lactating women, and patients with weakened immune systems may be resistant to topical therapy. Itching may continue for two to three weeks after treatment, but this does not mean there is still infestation. Additional medication can be used to treat the itching symptoms. Treatment is considered successful if no new burrows or rashes occur after forty-eight hours.

Additional steps may be necessary to avoid transmission or reinfestation. Any clothing or linens that have been in skin-contact with the patient within forty-eight hours should be machine washed and dried with hot air to kill mites and eggs. Dry cleaning is also effective. If live mites are observed after treatment, weekly treatments can be performed, however treatment usually only fails if the patient does not properly use the cream.