Scabies

Scabies (you say, skay-bees) is a skin infection caused when a tiny insect (called a mite) burrows under the skin surface, causing a very itchy rash.

Infection is easily spread from person to person through direct skin contact. It is important to treat scabies as it won't go away on its own.

Key points: 

  1. Scabies is caught through skin-to-skin contact with an infected person, or through shared bedding or clothing.
  2. You need to treat scabies with a special medicated lotion or cream.
  3. Everyone who lives in the same household with the infected person need to be treated.
  4. The itch may continue for weeks even though the mite is gone.
  5. See your doctor if itchiness continues longer than 6 weeks.

Causes

Scabies infestation starts when a pregnant female scabies mite comes into contact with a new host (you!). The female mite burrows into the outside layers of the skin where she lays up to 3 eggs each day for her lifetime of one to two months. The development from egg to adult scabies mite takes about 10 to 14 days.

The itchy rash experienced with scabies is due to an allergic reaction to the mite.

How do you get scabies?

Scabies is not due to poor hygiene. Anyone can get scabies, even the cleanest people. Washing with soap will not prevent or cure it. Scabies can be transferred by:

  • close body contact such as hugging, holding hands
  • sharing bedding or clothing.

Scabies is not caused by animal mites, which do not infest humans. However, animal mites can be responsible for bites on exposed sites, usually the forearms.

Symptoms

  • Scabies causes a very itchy rash which is normally worse at night or when warm. The itching begins a few days after infestation. It may occur within a few hours if the mite is caught a second time.
  • Scabies rash appears as tiny red, intensely itchy, bumps on the body, arms and legs. It can easily be confused with dermatitis or hives.
  • Burrows appear as tiny, grey, irregular tracks between the fingers and on the wrists. They may also be found in armpits, buttocks, on the genitals, insteps and backs of the heels.
  • Itchy lumps or nodules may be found in the armpits and groin or on the genitals. Nodules may stay for several weeks or longer after all living mites have been killed.
  • Blisters and pustules on the palms and soles are often found on infants with scabies.
  • Secondary infection commonly complicates scabies and results in crusting patches and scratched pustules.
  • Cellulitis may also occur, resulting in localised painful swelling and redness, associated with fever.

Diagnosis

Scabies may be suspected if there:

  • is severe itch that is particularly bad at night
  • a rash, that may look like tiny curving tracks with small blisters at one end
  • has been close contact with another itchy person.

To diagnose scabies your doctor will check your skin, particularly around the wrists, finger webs and on the sides and soles of the feet for redness, blisters, scratches and scabs that are typical of scabies infestation.

Other ways to diagnose scabies include:

  • Ink burrow test: Your doctor rubs a non-toxic washable felt-tip pen across the itchy areas. After a few moments the surface ink is wiped off. Any burrows present will absorb the ink and be seen as a dark, zig-zag line.
  • Skin scrapings: Sometimes your doctor may gently scrape some dry skin from the infected area and look at it under a microscope for signs of mites.

Crusted scabies (also called 'Norwegian scabies')

This a very contagious type of scabies in which there are thousands of mites, but very little itch. The main symptom is a widespread scaly rash which is frequently misdiagnosed as psoriasis.

Crusted scabies is the usual cause of outbreaks of scabies in institutions such as a hospitals, rest homes or prisons.

People in contact with someone with crusted scabies must be treated just in case they are carrying the mite.

Treatment

Scabies will not go away on its own. It needs to be treated with a special cream or lotion that contains an insecticide to kill the scabies. You can buy this from your pharmacy or get it on prescription from your doctor.

Children under 2 years of age and pregnant women should see their doctor for advice before treatment.

How to apply treatment

Everyone in the house must be treated at the same time - even if they are not itchy.

The best time to apply the cream/lotion is just before going to bed:
  • First have a warm shower or bath.
  • Then cover the whole body with the cream/lotion, from the chin to soles of the feet, including between fingers, under the nails and on the genital region.
  • Leave the cream/lotion on overnight.
  • If you wash your hands during the night the cream must be reapplied.
  • In the morning have a shower and wear clean clothes.

Linen and clothing

On the morning following treatment:

  • wash all clothing anyone has worn in the past week in hot water (or have it dry cleaned)
  • wash everyone's bedding and linen - pillowcases, sheets, towels and facecloths - in hot water.                        

Seek advice before repeating treatments

It may be necessary to repeat the scabies treatment – talk to your pharmacist or doctor for advice. Do not repeat treatment more than two times without medical advice. Overuse of insecticides will irritate the skin.

Itch improvement and persistent rash

Most people's itch improves within a few days of treatment. For others it can take 4 to 6 weeks for the itch and rash of scabies to clear completely even though every mite has been killed. Reasons for this include:

  • Scabies nodules may take several months to settle down. A topical steroid applied to each bump may help.
  • Dermatitis may have been caused by the mite, the scratching, the treatment or other factors. Treat itchy patches with emollients and mild topical steroids.
  • The diagnosis may be incorrect. Scabies can be confused with a number of other skin conditions, particularly dermatitis and hives.
  • Re-infestation or resistance to treatment. Scabies occasionally appears to be resistant to the prescribed scabies treatment. Talk to your doctor - you may need a different treatment.

Why treatment is important

Scabies will not go away without treatment. Complications can include:

  • scratching a lot can lead to serious skin infections and can cause scarring
  • untreated skin infections can lead to kidney and blood infections
  • children scratching a lot find it hard to concentrate and learn
  • preschool and school teachers can ask that children with untreated scabies be kept at home.

Learn more

Scabies Derm Net NZ, 2008
Scabies summary, symptoms, treatment, prevention NZ Ministry of Health

Credits: Editorial team. Last reviewed: 19 Jan 2015