Scabies

If you would like to know about the symptoms and diagnosis of scabies, and scabies treatment, you will find the following information of interest.

Scabies is a skin condition caused by a tiny mite. It usually causes a typical itchy rash. It can affect anyone of any age. It can be passed on to others by close skin-to-skin contact, most commonly by holding hands. Treatment with a cream or lotion will usually cure scabies, but you need to apply it properly to every part of your body. Two applications of treatment are needed, seven days apart.

What causes scabies?

Scabies is a skin condition caused by a mite (like a tiny insect) called Sarcoptes scabiei. The female mites tunnel into the skin and lay eggs. The eggs hatch into mites after a few days. Most of the symptoms are due to a skin reaction to the mites. Scabies is common. In the UK, about 1 in 1,000 people develop scabies each month.

How do you get scabies?

You need close skin-to-skin contact with an infected person to catch scabies. Most cases are probably caught from holding hands with an infected person. The hand is the most common site to be first affected. Close skin-to-skin contact when having sex is another common way of passing on the mite. The skin-to-skin contact needs to be for a reasonable time to catch the mite. Therefore, you are unlikely to catch scabies from an infected person by casual short contact such as a handshake or a hug.

The mites live in skin but die after a short time if they are away from the skin. Therefore, you are unlikely to catch scabies from bedding, towels, etc, unless you use them immediately after being used by someone with scabies. However, to play safe, it is best to treat bedding, towels, etc, as described later on.

Sometimes outbreaks of scabies occur in nurseries, residential homes, etc, where people are in regular close contact.

What are the symptoms of scabies?

• Mite tunnels (burrows) may be seen on the skin as fine, dark, or silvery lines about 2-10 mm long. The most common areas where they occur are the loose skin between the fingers, the front of wrists, and the hands. However, they can occur on any part of the skin. You may not notice the burrows until a rash or itch develop.
• Itch is often severe. Itch tends to be in one area at first (often the hands), and then spreads to other areas. The itch tends to be worse at night and after a hot bath.
• A rash usually appears soon after the itch starts. It is typically a blotchy, lumpy red rash that can appear anywhere on the body. The rash is often most obvious on the inside of the thighs, parts of the abdomen and buttocks, armpits, and around the nipples in women. The look of the rash is often typical of scabies. However, some people develop unusual rashes which may be confused with other skin conditions.
• Scratching sometimes causes slight skin damage. In some cases the damaged skin becomes infected by bacteria - a 'secondary' skin infection. If skin becomes infected with bacteria it becomes red, inflamed, hot, and tender.

Note: the itch and rash of scabies are due to an allergy (reaction) to the mites. These symptoms usually take 2-6 weeks to occur after you are first infected (as the allergy develops). The itch and rash can develop on any part of the skin, away from where the mites are actually burrowing. So, at first, you may not know that you are infected until a widespread itch and rash develop. You may pass the mite on to others before you have any symptoms.

Some people believe that they are 'covered in mites'. This is usually not so. Commonly there are just a few mites on the skin and just a few burrows. However, the allergy to the mites can cause you to itch all over, and for a rash to appear on many parts of the body.

The picture above shows some typical mite tunnels (burrows) either side of the wrist skin crease. It does not show the typical rash that occurs as a reaction to the mites.

Symptoms with a recurring infection

As mentioned above, the itch and rash normally take 2-6 weeks to develop when you have a first scabies infection. However, if you have a bout of scabies, have it treated and cleared, and then get it again, the symptoms may be slightly different. The itch and rash tend to develop within 1-3 days of being infected with the mite. This is because you are already sensitised to the mite from the first infection. So, your body reacts with the itch and rash much sooner than after a first infection.

How is scabies diagnosed?

Scabies is usually diagnosed by the typical symptoms and skin rash described above. Often, a doctor will find one or more mite burrows on the skin to confirm the diagnosis. It is sometimes difficult to tell the difference between the rash caused by scabies and some other skin conditions. Therefore, a scraping from the skin is sometimes sent to the lab to look for mites under the microscope if there is doubt about the diagnosis.

If itching and a rash develop in several people who live in the same home at about the same time then scabies is a likely cause.

Who should be treated?

Scabies will persist indefinitely if not treated. Treatment is needed for:

• Anybody who has scabies AND ...
• All household members, close contacts, and sleeping / sexual partners of the affected person - even if they have no symptoms. This is because it can take up to six weeks to develop symptoms after you become infected. Close contacts may be infected, but have no symptoms, and may pass on the mite.

Note: everyone who is treated should be treated at the same time - that is, on the same day.

What is the treatment for scabies?

Scabies is curable. The usual treatment is with permethrin 5% dermal cream. Permethrin is an insecticide that kills the mites. If permethrin cannot be used, an alternative is to use a lotion called malathion 0.5% aqueous 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. 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.

The following is a general guide about treatment which gives tips for success.

• You need to treat all the skin of your body (including the back, soles of the feet, between fingers and toes, under fingernails, scalp, neck, face, ears, and genitals). This may be different from what is said on the the package information. The package may say to only apply from the neck down for adults. However, national guidelines recommend that all the skin is treated. Pay special attention to the areas where mite burrows most commonly occur. That is, the front of the wrists and elbows, beneath the breasts, the armpits, and around the nipples in women.
• An adult needs at least 30g of cream or 100ml of lotion to cover the whole body. So, for two applications you will need at least 60g of cream or 200ml of lotion per adult.
• Apply cream or lotion to cool dry skin (not after a hot bath).
• The cream or lotion should be left on for the full recommended time. This time can vary depending on which one you use. For example, it is 8-12 hours for permethrin cream and 24 hours for malathion lotion.
• Children should stay off school until the first application of treatment has been completed.
• If you wash your hands or any other part of your body during the treatment period, you should re-apply the cream or lotion to the washed areas.
• Breastfeeding mothers should wash off the lotion or cream from the nipples before breastfeeding, and re-apply treatment after the feed.
• Put mittens on babies to stop them licking the cream or lotion off their hands.
• Clothes, towels, and bed linen should be machine washed at 50 degrees Celsius (50°C) or above after the first application of treatment. This kills any mites that may be present. Keep any items of clothing that cannot be washed in plastic bags for at least 72 hours to contain the mites until they die. An alternative option to kill any mites on clothes and linen are: ironing the item with a hot iron, dry cleaning, or putting items in a dryer on the hot cycle for 10-30 minutes. It is not necessary to fumigate living areas or furniture, or to treat pets.
• Some people who develop a secondary skin infection may also need antibiotics.

See a doctor if the itch persists longer than 2-3 weeks after treatment. Sometimes the first treatment does not work, and a different one is then needed. However, the common reasons why treatment fails, or for scabies to recur, are:

• the cream or lotion is not put on correctly for the full time, or
• a close contact is not treated at the same time, and the infection is passed back.

Note: you will still be itchy for a while after successful treatment

It is normal to take up to 2-3 weeks (and sometimes up to six weeks) for the itch to go completely after the mites have been killed by treatment. Also, even after successful treatment, in a small number of cases there remains some itchy brownish red lumps (nodules) up to 2cm in diameter. If these remain they most commonly occur on the genitals and arm pits. These lumps are not infectious or mean that the mite is still present. They occur in some cases as a prolonged skin reaction to the scabies mite. If they occur they usually go within three months, but occasionally last up to one year.

Treatment for itch

While waiting for the itch to go after killing the mites, you may wish to try something to ease the itch. A pharmacist can advise. Options include the following:

• 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 under three years old).
• Hydrocortisone cream. This is a mild steroid cream that may ease any inflammation and help ease itch.
• 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).

Crusted scabies (Norwegian scabies)

This type of scabies is unusual, and most people who develop scabies do not get this more severe form. Crusted scabies is an infection with many thousands of mites. It mainly occurs in people who have a poor immune system. For example, people with HIV/AIDS, people on chemotherapy, etc. It occasionally develops in frail people who are elderly or ill with other conditions. The condition causes a crusting skin rash similar to psoriasis. It can be extensive and severe and lead to serious secondary bacterial infections.

Because of the heavy infestation with the mite, people with crusted scabies are very contagious. However, healthy people will normally develop 'normal' scabies (described earlier) if they become infected from someone with crusted scabies.

References

• CKS Topic Review. Scabies (2007)
  
• British Association for Sexual Health & HIV Management of scabies (2001)
  
• Health Protection Agency Guidelines on the Management of Communicable Diseases: Scabies, (2003)
   

© EMIS and PiP 2007    Updated: 13 Jun 2007   DocID: 4325   Version: 38

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