Scabies

Scabies is a contagious skin condition that causes intense itching. It is caused by tiny mites called sarcoptes scabiei, which burrow into the skin.

Scabies can be spread through close physical contact and, less commonly, through secondary contact with clothes and bed linen.

How common is scabies?

Scabies is particularly widespread in countries that have a high population density and limited access to medical care. It is hard to estimate the exact number of cases in England and Wales because many people treat the condition themselves without visiting their GP.

However, one study suggested that one in every 1,000 people will develop a scabies infection each month.

Scabies is more common in children and women and appears to be more widespread in the north of England. Most outbreaks of scabies occur in winter, possibly because during this time of year people spend more time indoors and are in closer proximity to each other.

For reasons that are not fully understood, outbreaks of scabies seem to follow a cycle, with the number of cases peaking every 20 years.

What do they do?

Mites like warmth and smell. The mites feed by using their mouth parts and front legs to dig into the outer layer of the skin. They ingest tissue and fluids as they burrow. As they feed within the skin layer, they lengthen their burrows horizontally (about 0.5mm per day). The females lay two to three eggs per day in a permanent burrow in the skin. The larvae (or baby mites) hatch from the eggs in three to four days and travel to the skin surface where they lie in shallow pockets before they turn into adult mites.

Scabies like warmer places on the skin such as skin folds, between the fingers or under fingernails, around the buttock or breast creases. They also tend to hide under watch straps or bracelets, and in the skin on the finger under rings.

Treating scabies

Scabies is not usually a serious condition, but the intense itching can be unpleasant and have an adverse effect on the quality of life.

Scabies can usually be successfully treated using special creams. In order to prevent re-infection, it is important that all members of the household are treated, as well as any sexual partners that you have had.

Occasionally, scabies can lead to a secondary skin infection as the skin can become irritated and inflamed through excessive itching.

Crusted scabies

A more severe and uncommon form of the condition occurs when there are a lot of mites, sometimes thousands and millions, in the skin. This is called crusted scabies, and can affect older people and people with certain illnesses that lower immunity, such as HIV. See the 'complications section' for more details about crusted scabies.

If you have never had scabies before, the symptoms will begin 2-6 weeks after you are initially infected by the scabies mite. This is because your immune system -which is thought to produce the symptoms of itchiness associated with scabies - needs time to react to the infection.

If you have had scabies in the past, your symptoms will begin within 48 hours of infection because your immune system will have 'learnt' to react to a scabies infection.

Scabies causes your skin to feel intensely itchy. The symptoms tend to be worse at night, and after a hot shower, or bath.

The scabies mites will also leave small red blotches and lines on your skin, which are the marks caused by them burrowing into your skin.

Burrow marks can be found anywhere on the body but, in adults, they typically appear on:

• the folds of skin between your fingers,
• your wrists,
• your armpits,
• around your waist,
• the inside of your elbow,
• your buttocks,
• the soles of your feet,
• your knees,
• your shoulder blades,
• around your breasts (in women), and
• around your genital area (in men).

In infants and young children, burrow marks tend to appear at different locations around their body including the:

• face,
• head,
• neck,
• trunk,
• scalp.
• palms of the hands, and
• soles of the feet.

The life cycle of the scabies mite

Scabies is caused by the human parasite known as sarcoptes sabiei. An infestation starts when a female mite burrows into your skin. The mite can burrow into your skin within 30 minutes.

Male mites move between different burrow sites looking to mate with an unfertilised female. Once mating has taken place, the male mite dies and the female mite begins to lay eggs, which will hatch in approximately 3-4 days. The eggs take 10-15 days to grow into adult males, or females.

Without effective treatment this life cycle can continue indefinitely. Scabies mites are resistant to soap and hot water, and they cannot be scrubbed out of the skin.

The exact cause of the intense itchiness that is associated with scabies is unknown, but most experts believe that the itchiness is caused by the immune system reacting to the mites, and their saliva, eggs, and faeces.

How scabies is transmitted

Scabies mites cannot fly, or jump, so they can only move from one human body to another if two people have direct and prolonged physical contact. For example:

• prolonged hand holding,
• sexual intercourse, or
• sharing a bed.

Transmission by brief and limited physical contact, such as a handshake, or a hug, is unlikely.

Scabies mites can survive outside the human body for between 24-36 hours, so it is possible to become infested by coming into contact with contaminated clothes, or bed linen. However, this is a far less common way of acquiring the condition.

Scabies infestations can quickly spread because people are usually unaware that they have the condition until 2-6 weeks after the initial infection has taken place. In confined environments, such as schools, or nursing homes, where people are in close proximity to one another, there is an increased risk of catching scabies.

People often regard scabies as a condition that results from poor personal hygiene and living conditions, but there is no evidence that this is the case. Scabies can affect people from all walks of life.

Your GP will usually be able to diagnose scabies from the appearance of your skin, and by looking for the burrow marks

Testing for scabies burrow marks

The burrows of scabies mites can be highlighted by using an ink test. The ink is rubbed around an area of itchy skin, and is then wiped off using an alcohol pad. If scabies burrows are present, some of the ink will remain and will have tracked into the burrows, showing up as a dark line.

To confirm the diagnosis, a sample of skin may be gently scraped from the affected area, for examination under a microscope. The sample will be used to look for the mites, their eggs, and their faeces.

A diagnosis can often be confidently made if more than one family member has the same symptoms.

Where can I get a check-up?

There are a number of services you can go to. Choose the service you feel most comfortable with. A test can be done at:

• A genito-urinary medicine (GUM) or sexual health clinic. These clinics offer a free and confidential service. Their medical staff have specialist facilities for testing and systems for contacting, testing and treating sexual partners.
• Your general practice. Ask your GP or practice nurse.
• If you think you have scabies or have been in contact with someone who has scabies, you can go to a pharmacy for advice and treatment. If you do decide to treat yourself, you may want to consider having a sexual health check at some point, to make sure you don’t have an STI.

Do I have to pay for a test?

Not if you go to a GUM clinic or sexual health clinic. If you go to your GP, you may have to pay a prescription charge for treatment.

Although over-the-counter (OTC) treatments are available for scabies, it is recommended that you visit your GP if this is the first time you have had a scabies infestation. This is because other, more serious skin conditions can cause similar symptoms to scabies. It is therefore important for your GP to rule these out as a cause of your symptoms.

However, if another member of your household has already been diagnosed with scabies, you will not need to visit your GP and should proceed with treatment.

Creams and lotions

The two most widely used treatments for scabies are permethrin cream and malathion lotion. Permethrin is usually recommended first, and malathion lotion is used if the permethrin cream proves ineffective. Both medications contain insecticides that kill the scabies mite.

Applying the medication

It is important that all members of your household, and any close contacts (including all your sexual partners over the last six weeks or, if you have had scabies before, any sexual person that you have had sex with within the previous 48 hours), are treated at the same time, even if they do not have any symptoms. If they are not treated, re-infection could occur.

• Treatment should be applied to cool, dry skin and not after a hot bath (applying after a hot bath increases absorption into the body and removes the drug from the treatment site).
• Apply it to the whole body from the chin and ears downwards, paying particular attention to the areas between the fingers and toes and under the nails and areas where there are skin folds. Treatment can be massaged under fingernails and toenails using an old toothbrush (which should be sealed in a bag and thrown away afterwards).
• People with a weak immune system, the very young and elderly people should apply the treatment to the whole body including the face and scalp.
• Permethrin needs to be left on for eight to 12 hours.
• Malathion needs to be left on for 24 hours.
• If you wash during this time (for example, washing your hands), you should reapply the treatment.
• Follow-up treatment after seven days is advised to make sure the treatment is successful. This is to ensure that any mites that have hatched from existing eggs will be killed by the second application.

If you are breastfeeding, the cream or lotion will need to be thoroughly washed off before feeds and reapplied if necessary.

You should talk to your GP or pharmacist about using Malathion on children under six months and before using Permethrin on children aged below two years.

If you are embarrassed about contacting your previous sexual partners, your GP surgery may be able to inform anyone who may have been affected that they may have been exposed to scabies, without giving them your identity.

Infection control

On the same day that you first apply the cream, you should also wash all clothes, bed linen, and towels, at a temperature of above 50C (122F). If you are unable to wash certain items, place them in a plastic bag for at least 72 hours, by which time the mites will have died. It is not necessary to fumigate furniture, pets, or carpets.

If you have been diagnosed with scabies, you should avoid any close and prolonged physical contact with other people until you have applied the cream for the first time. You should also avoid close contact with other household members until their treatment has been completed.

Children and adults can return to school, or work, after the first application of cream has been completed.

Itchiness

Your GP should also be able to prescribe creams, such as a mild steroid creams, that can help relieve the symptoms of itchiness. The over-the-counter (OTC) remedy, camomile lotion, may also help to relieve itchy skin.

Oral antihistamines can help to control symptoms of itching and help with sleeping. These can be bought over- the counter (OTC) at your local pharmacy. However, they might cause drowsiness, so avoid driving, or operating heavy machinery, if you are affected in this way. If you unsure, check with your GP, or pharmacist.

The symptoms of itchiness can persist for several weeks after treatment because your immune system is still reacting to the presence of dead mites and their waste products. See your GP if the symptoms of itchiness persist for more than six weeks.

Side effects of treatment

• Permethrin 5% dermal cream

Side effects can include itching, numbness, a tingly feeling, stinging on application or skin irritation. You should talk to your GP or pharmacist if these side effect don’t go away.

• Malathion 0.5% aqueous liquid

Skin irritation can occur. You should talk to your GP or pharmacist if this worsens or doesn’t go away.

There is no evidence that complementary therapies can cure scabies.

There is no evidence that complementary therapies can cure scabies.

If you delay seeking treatment you risk passing the condition on to someone else.

You should avoid sex or close body contact until you and your partner have both completely finished the treatment, otherwise you could be reinfected.

Crusted scabies

Crusted scabies (which is also sometimes referred to as Norwegian scabies) is a more severe form of scabies that affects people who have a weakened immune system.

People who may have a weakened immune system include:

• the very young,
• the very old,
• people with a condition that affects their immune system, such as HIV,
• people who are taking steroids to treat other medical conditions, and
• people undergoing chemotherapy.

Research has found that a healthy immune system seems to interrupt the reproductive cycle of the scabies mite. For example, most people who are affected by the condition will only have between 5-15 mites on their body at any one time.

However, if your immune system is weakened, the number of scabies mites can increase dramatically. People with crusted scabies can have literally millions of scabies mites in their body at any one time. The increase in the number of mites causes the appearances of thick, warty crusts to appear on the skin.

Due to the high number of scabies mite, crusted scabies is highly contagious. However, transmission from someone with crusted mites will only lead to the normal type of scabies in those with a healthy immune system. Even minimal physical contact with a person with crusted scabies, or their bed linen, or clothes can lead to infection.

As strict controls are required to limit the spread of crusted scabies, the condition may need to be treated in hospital.

Crusted scabies can be treated by using insecticide creams, or a medicine called ivermectin, which is taken orally (as a tablet). Ivermectin kills the mites by stopping their nervous system from working.

Secondary infection

Excessive itching of the skin can break the surface of the skin and make it vulnerable to a bacterial infection, such as impetigo (a highly contagious bacterial infection). Antibiotics may be required to control any secondary infection.

Scabies has been known to worsen other pre-existing skin conditions, such as eczema. However, if you have another skin condition, it should settle down once the scabies has been successfully treated.

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Strong M., Johnstone P.W. (2007). Interventions for treating scabies. Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD000320. DOI: 10.1002/14651858.CD000320.pub2.