Scabies is an itchy skin condition caused by an infestation by the itch mite Sarcoptes scabiei. They are tiny, just 1/3 millimeter long, and burrow into the skin to produce intense itching, which tends to be worse at night. The mites that cause scabies are not visible with the naked eye but can be seen with a magnifying glass or microscope.

Scabies mites are very sensitive to their environment. They can only live off of a host body for 24-36 hours under most conditions. Transmission of the mites involves close person-to-person contact of the skin-to-skin variety. It is hard, if not impossible, to catch scabies by shaking hands, hanging your coat next to someone who has it, or even sharing bedclothes that had mites in them the night before. Sexual physical contact, however, can transmit the disease. In fact, sexual contact is the most common form of transmission among sexually active young people. However, other forms of physical contact, such as mothers hugging their children, are sufficient to spread the mites. Over time, close friends and relatives can contract it this way, too. School settings typically do not provide the level of prolonged personal contact necessary for transmission of the mites.

Scabies produces a skin rash composed of small red bumps and blisters and affects specific areas of the body. Scabies may involve the webs between the fingers, the wrists and the backs of the elbows, the knees, around the waist and umbilicus, the axillary folds, the areas around the nipples, the sides and backs of the feet, the genital area, and the buttocks. The bumps (medically termed papules) may contain blood crusts. It is helpful to know that not every bump is a bug. In most cases of scabies affecting otherwise healthy adults, there are no more than 10 or 15 live mites even if there are hundreds of bumps and pimples.
The scabies rash is often apparent on the head, face, neck, palms, and soles of the feet in infants and very young children but usually not in adults and older children.

Most cases of scabies can be diagnosed by describing the symptoms to the doctor and by examination of the skin. There is no blood test for scabies.

Sometimes, the doctor will do a skin scraping to make or confirm the diagnosis. This is performed by placing a drop of oil or saline on top of an affected area. Then using a scalpel, the area is scraped, and the material that was collected is placed on a slide to examine under a microscope. The doctor will look for the mite or its eggs.

Often, there are very few mites that can be hard to find. Therefore, even if the scrapings are negative, the doctor may still recommend treatment if he or she is very suspicious that scabies is present.

Curing scabies is rather easy with the administration of prescription scabicide drugs. There are no approved over-the-counter preparations that have been proved to be effective in eliminating scabies. The following steps should be included in the treatment of scabies:

1.    Apply a mite-killer like permethrin. These creams are applied from the neck down, left on overnight, then washed off. This application is usually repeated in seven days. Permethrin is approved for use in people 2 months of age and older.

2.    An alternative treatment is 1 ounce of a 1% lotion or 30 grams of cream of lindane, applied from the neck down and washed off after approximately eight hours.

3.    Ivermectin, an oral medication, is an antiparasitic medication that has also been shown to be an effective scabicide, although it is not FDA-approved for this use. The CDC recommends taking this drug at a dosage of 200 micrograms per kilogram body weight as a single dose, followed by a repeat dose two weeks later. Although taking a drug by mouth is more convenient than application of the cream, ivermectin has a greater risk of toxic side effects than permethrin and has not been shown to be superior to permethrin in eradicating scabies. It is typically used only when topical medications have failed or when the patient cannot tolerate them.

4.    Crotamiton lotion 10% and cream 10% (Eurax, Crotan) is a another drug that has been approved for the treatment of scabies in adults, but it is not approved for use in children.

5.    Antihistamines, such as diphenhydramine (Benadryl), can be useful in helping provide relief from itching.

6.    Wash linens and bedclothes in hot water. Because mites don't live long away from the body, it is not necessary to dry-clean the whole wardrobe, spray furniture and rugs, and so forth.

7.    Treat sexual contacts or relevant family members (who either have either symptoms or have the kind of relationship that makes transmission likely).

Just as the itch of scabies takes a while to reach a crescendo, it takes a few days to subside after treatment. After a week or two, relief is dramatic. If that doesn't happen, the diagnosis of scabies must be questioned.

Crusted scabies
Crusted scabies is a more severe form of scabies that affects people who have a weakened immune system.
People who may have a weakened immune system include:

• The very young,
• The very old,
• People with a condition that affects their immune system, such as HIV,
• People who are taking steroids to treat other medical conditions, and
• People undergoing chemotherapy.

Due to the high number of scabies mite, crusted scabies is highly contagious. However, transmission from someone with crusted mites will only lead to the normal type of scabies in those with a healthy immune system. Even minimal physical contact with a person with crusted scabies, or their bed linen, or clothes can lead to infection.
As strict controls are required to limit the spread of crusted scabies, the condition may need to be treated in hospital.
Crusted scabies can be treated by using insecticide creams, or a medicine called ivermectin, which is taken orally .Ivermectin kills the mites by stopping their nervous system from working.

Secondary infection
Excessive itching of the skin can break the surface of the skin and make it vulnerable to a bacterial infection, such as impetigo (a highly contagious bacterial infection). Antibiotics may be required to control any secondary infection.
Scabies has been known to worsen other pre-existing skin conditions, such as eczema. However, if you have another skin condition, it should settle down once the scabies has been successfully treated.

Not having close skin-to-skin contact with someone who has scabies or with their personal items (such as clothes, towels, and brushes) will help you avoid getting scabies. People who have scabies are encouraged to use care to prevent spreading the mites to others.