Scabies is a skin infestation with a mite called Sarcoptes scabiei. These mites burrow into the skin where they live and reproduce. Eggs laid in the burrows hatch, crawl out onto the skin and make new burrows.
The skin infestation usually involves the genital areas, buttocks, lower abdomen, wrists, forearms and webs between the fingers. Burrows are often difficult to see, but can most often be seen on the webs between the fingers, around the waist (under the belt line), in the creases of the wrists and elbows, and on the palms and soles of the feet.
In people without previous exposure to scabies, it takes 2–6 weeks after the first infestation for symptoms to appear. Mite droppings in the skin cause an itchy reaction, which may be severe. The itch is often worse at night and after a hot shower or exercise. There may be raised red lumps. Scratching can remove the tops of these lumps causing open sores, which can become infected.
In people who have been previously infested, a new infestation will cause symptoms within 1-4 days of exposure. Heavy infestation can cause extensive scaling and crusted warty lesions of the skin called “Norwegian” or “crusted” scabies. This type of infestation is highly transmissible. In people with a depressed immune system and older persons infestation often appears as a generalised dermatitis more widely distributed than the burrows.
Ask your doctor to recommend an appropriate treatment. The instructions need to be followed carefully to make sure it works without causing any harm. Other household members and sexual contacts should be treated at the same time.
Treatment usually requires application of a cream or lotion which is repeated after seven days. As mites can live for a day on clothing and bed linen, clothes and sheets should be washed on a hot cycle on the day of treatment. Mattresses and pillows should be put out in the sun for two or three hours. Blankets can be put in a sealed bag for three days, after which time any mites will have died. Insect spray can be used on soft furniture (eg. lounge chairs) to kill mites.
It is common for the itch to persist for several weeks after treatment. Antihistamines can help to reduce the itch and prevent scratching. Creams (available from a pharmacy) can also help reduce the itch. Do not over-treat as the skin may become irritated.
If not treated, scabies causes ongoing irritation, sores may become infected, and it remains transmissible to other people. The mite does not transmit any infectious disease.
Scabies is passed from person to person through prolonged direct contact with infested skin. It can be spread by sexual contact, as well as by non-sexual contact in families, groups and institutions. Transfer from clothes and bedclothes can occur if these have been contaminated by infested persons within the previous 24 hours for normal scabies and 48 hours for Norwegian scabies. Mites can burrow beneath the skin surface in about one hour. Mites can survive for two days away from the human body although high temperatures will kill them more quickly.
Use of condoms does not prevent scabies being passed from one person to another during sexual activity.
Any person with itchy lumps or sores in the genital area should not have sex or close contact with another person until they have received advice from their doctor.
For further information please contact your local doctor, community health centre or nearest public health unit.
Heymann D (Ed). 2008. Control of Communicable Diseases Manual, 19th edition. Washington, DC: American Public Health Association. 540-543