What is scabies?
Scabies is a common and very itchy skin rash caused by a tiny mite called Sarcoptes scabiei. It can affect people of any age but is most common in the young and the elderly.
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What causes scabies?
The mites that cause scabies are tiny parasites which are smaller than a pinhead. They are usually spread by direct skin-to-skin contact with someone who already has scabies and sometimes, but rarely, from shared clothing, towels or bedding. People affected by scabies have an average of about a dozen adult mites on their skin; a few carry many more. Anyone can get scabies.
Rarely, a variant of scabies known as ‘crusted scabies’ (previously called Norwegian scabies) can occur in patients who have a poor immune system or who are elderly and ill due to other conditions. There are thousands of scabies mites on the skin in this variant and it is therefore highly contagious.
Scabies in animals called ‘mange’ is caused by a different type of mite and therefore cannot infect humans.
Is scabies hereditary?
No, but it is common for several members of a family to have scabies at the same time as it spreads easily when people live together.
What are the symptoms of scabies?
Itching is the main symptom of scabies and it often gets worse at night. It can take about a month for the symptoms to appear after being infected by the mites.
The itching can affect the whole body apart from the head and neck, although the elderly and infants may develop a rash on these areas. It is common for several people in the same family, and their friends, to become itchy at roughly the same time.
What does scabies look like?
The rash of scabies is a mixture of scratch marks and tiny red spots. Scratched areas may develop crusty sores which can become infected and develop into small pus-filled spots. A widespread rash similar to eczema is very common. The itchy rash can cover much of the body, but the mites are found mainly in the folds of skin between fingers and toes, the palms of the hands, the wrists, ankles and soles of the feet, groins and breasts. The scabies mites burrow into the skin in these areas to lay their eggs, leaving tiny spots and silver coloured lines on the skin. Adult mites are tiny, only about 0.4 mm long which when looking through a magnifying lens or dermatoscope, appear as a tiny dark dot at the end of a silver line.
How is the diagnosis of scabies made?
The doctor will usually be able to diagnose scabies on the basis of the history and examination of the rash. To confirm the diagnosis the doctor may wish to scrape off a small surface section of skin to be sent for examination under a microscope.
Can scabies be cured?
Yes, with the right treatment, it clears up quickly and completely; but if it is not treated, scabies lasts for months or even years. However, even after the mites have been killed by treatment, the itching usually carries on for a few weeks before settling.
How should scabies be treated?
The treatment of scabies involves using medication and making sure family members, friends and anyone who has been close contact with each other are all treated at the same time, even if they do not have any symptoms, as a precaution.
Several preparations are effective in the treatment of scabies. Of these, permethrin cream and malathion liquid are used most commonly in the U.K. It is worth checking that the prescribed preparation is the one especially designed for scabies, as both agents are available in several formulations which are useful only for head lice. The doctor may suggest different preparations for women who are pregnant or breast-feeding, or for babies.
What can I do?
Follow the instructions issued with your treatment in detail; they will be based on the following principles:
- The mites may be anywhere on the skin, so the treatment must be applied to all areas of skin below the neck in adults, all areas of skin in children including the scalp, and not just to the itchy parts.
- The treatment should be left on for at least 12 hours before being washed off.
- When washing hands or any part of the body, treatment should be re- applied to the washed areas again.
- Two treatments, one week apart, are necessary to kill the mites that have hatched from eggs after the first application.
- Bedding and clothing should be washed at a high temperature to destroy the mites. Items that can’t be washed or dry cleaned should be sealed in a plastic bag for at least 1 week or put in a freezer.
- Taking a bath before treatment is not necessary.
Finally, when scabies has been caught from a sexual partner, the doctor may want to check for the presence of other diseases that may have been picked up at the same time.
A recurrence of scabies is, unfortunately, quite common.
This information is provided by the British Association of Dermatologists.
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