Scabies

Page last reviewed: 13/07/2011

Scabies is a contagious skin condition where the main symptom is intense itching. It is caused by tiny mites called Sarcoptes scabiei, which burrow into the skin.

Scabies can be spread through:

  • skin-to-skin contact for long periods of time with someone who is infected
  • sexual contact with someone who is infected

Scabies can also be passed on through sharing clothing, towels and bedding with someone who is infected. However, this is less likely than getting the infection through skin-to-skin contact.

The incubation period (the time it takes for symptoms to show after infection) for scabies is up to eight weeks.

How common is scabies?

Scabies is particularly widespread in countries that have a high population density and limited access to medical care. The condition is present in the following tropical and subtropical areas at all times (endemic):

  • Africa
  • Egypt
  • Central and South America
  • northern and central Australia
  • Caribbean Islands
  • India
  • Southeast Asia 

In developed countries, outbreaks of scabies can sometimes occur in places where there are lots of people, such as schools, crèches or pre-schools and nursing homes. There can also be individual cases of scabies that are not isolated to one specific place. These cases are known as sporadic.

It is difficult to estimate the exact number of scabies cases in Ireland because many people treat the condition themselves using over-the-counter (OTC) medicines, without visiting their GP.

Most outbreaks of scabies in Ireland occur during the winter, which may possibly be because people tend to spend more time indoors and are in closer proximity to each other during this time of year. Outbreaks of scabies are also more common in cities.

Scabies mites

Sarcoptes scabiei mites like warmth and smell. The mites feed using their mouth parts and front legs to dig into the outer layer of the skin (epidermis). They ingest tissue and fluids as they burrow.

As the mites feed within the skin layer, they lengthen their burrows horizontally by about 0.5mm a day. The females lay two to three eggs a day inside the burrow. After three to four days, the larvae (baby mites) hatch from the eggs and travel to the surface of the skin where they lie in shallow pockets before maturing into adult mites. 

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

Outlook 

Scabies is not usually a serious condition, but the intense itching can be unpleasant and have an adverse effect on a person's quality of life. However, the itching that is caused by scabies can usually be effectively treated using topical treatments (skin creams).

Scabies can lead to a secondary skin infection if the skin becomes irritated and inflamed through excessive itching.

A more severe, but uncommon, form of scabies can occur in cases where there are a lot of mites in the skin. This is called crusted scabies, and can affect older people and those with a lowered immune system (the body's natural defence against illness and infection).

Page last reviewed: 13/07/2011

The main symptoms of scabies are:

  • intense itching that is worse at night
  • skin rash in the areas of the body where mites have burrowed

These symptoms are described in more detail below.

Intense itching

The main symptom of scabies is intense itching that is worse at night when the skin temperature is warmer. The itching may take between four to six weeks to develop because this is the length of time that it takes for the body to react to the absorption of mite droppings into the skin cells.

If you have had a previous infection, the symptoms will begin to show within one to two days. This is because your immune system will have learnt to react to a scabies infection.

Skin rash

The skin rash that is associated with a scabies infection is made up of tiny red insect bites or spots. If you scratch the rash, you may also develop crusty sores.

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

  • the folds of skin between the fingers and toes
  • the wrists
  • the elbows
  • around breast nipples (in women)
  • around the male genital area

The rash can also sometimes occur in the following areas:

  • the underarm area (axillae) 
  • around the waist
  • the inside of the elbow
  • the lower buttocks
  • the lower legs
  • the soles of the feet
  • the knees
  • the shoulder blades
  • female genital area
  • the nipples
  • the groin
  • around the ankles

Elderly people, young children and those with a low immune system (immunocompromised) may also develop a rash on their head and neck.

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

  • face
  • head
  • neck
  • scalp
  • palms of the hands
  • soles of the feet

The scabies mites also leave small red blotches and silver coloured lines on the skin. These marks are caused by the mites burrowing into the skin.

Blisters and pustules (small blisters that contain pus) on the soles of the feet and palms are also a common characteristic of scabies in infants.

Page last reviewed: 13/07/2011

The scabies mite life cycle

Scabies is a skin condition that is caused by the human parasite Sarcoptes scabiei. An infestation (the presence of animal parasites inside the body) starts when a female mite burrows into your skin.

Male mites move between different burrow sites looking to mate with an unfertilised female. After mating has taken place, the male mite dies and the female begins to lay eggs. The eggs hatch around three or four days later.

After the eggs have hatched, the young mites move to the surface of the skin where they mature into adults. It takes between 10 to 15 days for the mites to mature. The male mites stay on the surface of the skin, and the female mites burrow back into the skin in order to create a new burrow. The life cycle is then repeated.

Without effective treatment, the life cycle of the scabies mite 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 it is caused by the immune system reacting to the mites and their saliva, eggs and faeces (stools).

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, scabies mites can be transmitted by:

  • holding hands with someone who is infected for a prolonged period of time
  • having sex with someone who is infected
  • sharing a bed, towels or clothes (although this is rare)

Transmission through brief and limited physical contact, such as shaking hands or hugging someone, is unlikely.

Scabies mites can survive outside the human body for between 24 to 36 hours, so it is possible to become infected 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 spread quickly because people are usually unaware that they have the condition until two to three weeks after the initial infection has occurred. There is an increased risk of catching scabies in confined environments, such as schools and nursing homes, where people are in close proximity to one another.

People often regard scabies as a condition that is caused by poor personal hygiene and living conditions. However, there is no evidence to suggest that this is the case. Scabies can affect people from all walks of life, although certain groups have an increased risk of getting the condition.

Risk groups

Some groups of people have an increased risk of catching scabies because they are in close contact with lots of other people. Those with an increase risk include:

  • children - this is due to the outbreaks of scabies that can occur at schools and crèches or pre-schools
  • young mothers - who are in close contact with affected children
  • elderly people who live in nursing homes
  • people who are sexually active

Page last reviewed: 13/07/2011

Your GP will usually be able to diagnose scabies from the appearance of your skin, and by looking for the burrow marks that are made by the Sarcoptes scabiei mite.

However, as the scabies infection is spread very easily, it is often possible to make a confident diagnosis if more than one family member has the same symptoms.

Ink test

The burrows of scabies mites can be highlighted by using an ink test. The ink is rubbed around an area of itchy skin before being wiped off with 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.

In order to confirm the diagnosis, a skin sample may be gently scraped from the affected area so that it can be examined under a microscope for evidence of scabies mites and their eggs and faeces (stools).

Ruling out other conditions

Your GP will also want to rule out any other skin conditions that may be indicated by your symptoms, such as:

  • eczema - a chronic (long-term) skin condition that causes the skin to become red, dry, cracked and itchy
  • impetigo - a highly contagious bacterial infection of the surface layers of the skin

Check up

If you think you have scabies you can either see your GP or go to your nearest GUM (genito-urinary medicine) clinic, where you can be examined and receive advice and treatment.

If you do decide to treat yourself, you will need to have a full sexual health check to make sure you do not have any sexually transmitted infections (STIs). This is available from your nearest GUM clinic.

In order to prevent re-infection, it is important that all members of your household are treated, as well as any sexual partners that you have had over the last six weeks. If you have had scabies previously, anyone that you have had sex with in the previous 48 hours should be treated.

If you are embarrassed about contacting your previous sexual partners, your GP surgery may be able to inform anyone who has been exposed to scabies without giving them your identity. This service may also be available at your local GUM clinic.

 

What happens at a sexual health clinic?

  • When you attend a clinic, you will be asked for your name, date of birth and contact details and you will be registered as a patient. These details are confidential and will not be passed on to your GP unless you request it.
  • The clinic nurse will ask why you’ve attended the clinic.
  • You will be asked for a sexual history, which will include questions such as when you last had sex, whether you used condoms, whether you have had a sexually transmitted infection (STI) before, and if you're on any medication.
  • If you're attending a clinic for scabies, you may be offered tests for other STIs.  

Page last reviewed: 13/07/2011

Visit your GP immediately if you get scabies and you have not had a previous infection. If you delay treatment, you risk passing scabies on to someone else.

As other, more serious skin conditions can sometimes cause similar symptoms to scabies, your GP will need to rule these out as a possible cause of your symptoms.

If another member of your household has already been diagnosed with scabies, visit your GP or nearest GUM clinic to be examined and treated to avoid passing on the infection.

Avoid having sex and other forms of close bodily contact until you and your partner have both completed the treatment.

Creams and lotions

The two most widely used treatments for scabies are:

  • permethrin cream
  • malathion lotion

Permethrin cream is usually recommended as the first treatment. Malathion lotion is used if the permethrin cream proves to be ineffective. Both medications contain insecticides that kill the scabies mite.

Permethrin cream should be used under medical supervision for women who are pregnant and also for young children who are between two months and two years old. You should check with your GP before using this treatment.

Malathion lotion has no known affects on women who are pregnant or breastfeeding. However, you should also seek advice from your GP or pharmacist before using malathion lotion. Children who are six years old and under should be medically supervised while being treated with malathion.

Applying the medication

It is important that all members of your household, and any close contacts are treated at the same time as you, even if they do not have symptoms. Otherwise, re-infection could occur.

The following advice relates to how permathrin cream and malathion lotion should be applied.

  • Permathrin cream or malathion lotion should be applied to cool, dry skin and not after a hot bath. If the cream or lotion is applied when the body is hot, it will be absorbed quickly into the skin and will not remain on the area where the burrows are present.
  • 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).
  • Adults should not apply lotion above the neck. However, in children under two years old a thick layer should be applied to the scalp, face and ears, avoiding the eyes and mouth.
  • People with a weak immune system, the very young and elderly people should apply the treatment to their whole body, including their face and scalp.
  • If you wash your hands within 8-12 hours, reapply the cream to your hands, making sure that you also put it under your nails. 
  • Permethrin needs to be left on for 8-12 hours, and malathion should be left on for 24 hours. 
  • Follow-up treatment after seven days is recommended in order to make sure that the treatment is successful. This will ensure that any mites that have hatched from existing eggs will be killed by the second application.

Follow up

Contact your GP if the symptoms of itching do not improve after two weeks of treatment and you notice new burrows appearing on your skin. They may recommend that the treatment is repeated or prescribe a different lotion that you can use.

Side effects

You may experience side effects after using permethrin or malathion. Possible side effects of permethrin include:

  • itching
  • skin irritation
  • numbness
  • a tingly sensation
  • stinging on application

See your GP or pharmacist if these side effects persist.

Skin irritation can also occur after using malathion. Again, you should visit your GP or pharmacist if you have this side effect and it persists or gets worse.

Infection control

On the day that you first apply the cream, wash all clothes, bed linen and towels at above 50C (122F). If you are unable to wash certain items, place them in a plastic bag for at least 72 hours. After this time, the mites will have died. It is unnecessary to fumigate furniture, pets or carpets.

If you have been diagnosed with scabies, avoid any close and prolonged physical contact with others until you have applied the cream. 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 to relieve the symptoms of itchiness. Calamine lotion, which is available without a prescription, may also help to relieve itchy skin.

Oral antihistamines can also be used to help control the symptoms of itching, enabling you to get a better night's sleep. They can be bought at your local pharmacy.

However, oral antihistamines can sometimes cause drowsiness, so avoid driving or operating heavy machinery if you are affected in this way. If you are unsure, check with your GP or pharmacist.

You may continue to experience itchiness for a couple of weeks after your course of treatment has been completed. This is because your immune system will still be reacting to the presence of dead mites and their droppings. You should visit your GP if the symptoms of itchiness persist for longer than six weeks after treatment is complete.

Complementary therapies

There is no evidence to suggest that complementary therapies can effectively treat scabies.

Treatment for crusted scabies

Crusted scabies, in which thousands of mites may have infested the skin, can be more resistant to treatment and may require more than one treatment to remove all the mites. Your GP may refer you to a specialist to ensure that the most appropriate treatment is given.

Page last reviewed: 13/07/2011

Crusted scabies

Crusted scabies (also sometimes referred to as Norwegian scabies) is a more severe form of scabies where thousands, or even millions, of scabies mites are present.

Crusted scabies can begin as scabies before developing into the more severe form following a skin reaction. Crusted scabies affects all parts of the body, including the head, neck and nails. Unlike normal scabies, the rash of crusted scabies does not itch and it can affect the scalp.

In crusted scabies, the increase in the number of mites causes the appearances of thick, warty crusts to appear on the skin. The condition is often misdiagnosed as psoriasis (a skin condition that causes red, flaky, crusty patches of skin that are covered with silvery scales).

Crusted scabies affects people who have a weakened immune system (the body's natural defence against infection). People who may have a weakened immune system include:

  • the very young
  • people with brain disorders (neurological disorders, such as Parkinson's disease)
  • people with Down's syndrome, a genetic disorder caused by an abnormality in one of the chromosomes (genetic material) that occurs when a baby is still in the womb (uterus)
  • pregnant women
  • elderly people
  • people with a condition that affects their immune system, such as HIV or AIDs
  • people who are taking steroids to treat other medical conditions
  • people who are 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 5-15 mites on their body at any one time.

However, if your immune system is weakened, the number of scabies mites can increase significantly. People with crusted scabies can have thousands or millions of scabies mites in their body at any one time.

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

Crusted scabies can be treated by using insecticide creams, or a medicine called ivermectin, which is taken orally (by swallowing 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 your skin, making it more vulnerable to a bacterial infection such as impetigo (a highly contagious bacterial skin infection). Antibiotics may be recommended to control a secondary infection.

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

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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