Symptoms

• 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 10-15 live mites even if there are hundreds of bumps and pimples on the skin.

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.

Diagnosis

Scabies is suggested by the presence of the typical rash and symptoms of unrelenting and worsening itch, particularly at night. Ultimately, the definitive medical diagnosis is made when evidence of mites is found from a skin scraping test. By scraping the skin (covered with a drop of mineral oil) sideways with a scalpel blade over an area of a burrow and examining the scrapings microscopically, it is possible to identify mites, eggs, or pellets. This process can be difficult, however, since burrows can be hard to identify.

Sometimes scratch marks are mistaken for burrows, and even the examination of scrapings from 15 or more burrows may only reveal one or two mites or eggs. If the characteristic physical findings are present, scabies can often be treated without performing the skin scrapings necessary to identify the mites.

Causes

Scabies is very contagious, and direct skin-to-skin contact is the mode of transmission. 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, so risk factors include close contact with an infected person. 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, and scabies has been considered by many to be a sexually transmitted disease (STD).

However, other forms of physical contact, such as a mother hugging a baby, 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 the transmission of the mites.

Scabies is curable. The usual scabies treatment is with permethrin cream. Permethrin is an insecticide that kills mites. This is known to be the treatment that works the best. If permethrin cannot be used, an alternative is to use a lotion called malathion liquid. (For example, some people may be allergic to permethrin.)

You can buy both of these products from pharmacies. You can also get them on prescription from a doctor. They are easy to apply and normally work well if used properly.

Re-apply the same treatment seven days after the first application. This helps to make sure that all the mites are killed.

Itching can be a distressing symptom. It can be eased either with topical treatments that you apply to the skin (such as creams or lotions), or with medication taken by mouth. Cold moisturisers (emollients), especially if they contain menthol, can provide temporary relief. Avoid applying strong steroid creams, especially if the diagnosis of scabies is uncertain.

• Crotamiton cream or lotion has soothing qualities and may help to relieve itch. Apply crotamiton 2-3 times a day (but only once a day for children less than 3 years old).
• Hydrocortisone cream. This is a mild steroid cream that may ease any inflammation and help to ease the itch. It can be bought from the chemist, or obtained by prescription. It can be applied once or twice per day, for up to a week.
• An antihistamine medicine that makes you drowsy, such as chlorphenamine. This does not ease the itch directly, but can help you to sleep if itching is a problem at night (particularly for children). It is not licensed for this use but can be safely used under the direction of a doctor.

Norwegian scabies, or crusted scabies, is a severe form of scabies first described in Norway. Crusted scabies almost always affects people with a compromised immune system and is observed most frequently in the elderly, those who are mentally or physically disabled, and in patients with AIDS, lymphoma, or other health conditions that decrease the effectiveness of the immune response.

Due to the poor function of the immune system, an individual may become infested with hundreds of thousands of mites. The lesions of this distinctive form of scabies are extensive and may spread all over the body.

The elbows, knees, palms, scalp, and soles of the feet are most commonly the original sites of involvement, and the scaly areas eventually take on a wart-like appearance. The fingernails can be thickened and discoloured. Interestingly, itching may be minimal or absent in this form of scabies.

A particular danger of crusted scabies is that these lesions often predispose to the development of secondary infections, as with Staphylococcus or Streptococcus bacteria, including impetigo, a common skin infection of children.