What is Scabies?

Scabies is a skin infection that is caused by mites. It is very infectious, and usually causes severe itching and a rash. It is a very common condition found all over the world and anyone can get the infection. It will not go away without medical treatment, but it is easy to cure.

What Causes Scabies?

Scabies is caused by a mite called Sarcoptes scabei. The mite is a tiny creature, a little like an insect, but with 8 legs. It cannot be seen with the naked eye as it is less than half a millimetre big.

The mites feed on the skin, burrowing into it as they do. When the adult female is fertilised it lays eggs in these burrows, usually 2-3 eggs a day. Female mites die after laying the eggs, but after 3-4 days the eggs hatch into baby mites (larvae). The larvae live in shallow burrows which are closer to the surface. After another 4 days they become adult mites. These adult mites reproduce and the cycle continues.  

What Are The Symptoms of Scabies?

Symptoms of scabies usually only start around 2-6 weeks after you are first infested. Symptoms include:

  • Itching – This itching is thought to be caused by the body having an allergic response to the mites. It is very severe itching, and it is usually worse during the night. This can cause disturbed sleep. It can also be worse after a hot bath.
  • Rash – A red rash is usually associated with the itching. The rash is blotchy and bumpy and can appear anywhere on the body. It is also caused by an allergic response. The rash is often most noticeable around the buttocks, inner thighs, armpits and nipples. It also commonly affects elbows, knees, hands, wrists, the skin around the belly button, and the feet. The allergic response affects the whole body, so just because you have a widespread rash, this does not mean that there are mites all over the body. Normally, a person only has 10-15 mites living on them, in the burrows, yet the rash can appear in a variety of places.
  • Mite Burrows – The burrows that the mites make can sometimes be seen on the skin. They are tiny tracks on the surface of the skin, usually between 2 and 15 mm long. The tracks can be red, silver, or dark in colour, but often can be difficult to spot. Scabies tend to like warm areas, such as folds of skin, around the buttocks or breasts, the groin, and behind the knee. The most common place that the tunnels are found, however, is between the fingers. The mites also sometimes burrow under watch straps, bracelets and rings.  In children, the burrow marks can be found in different areas, including the scalp, head, face and neck, and the palms of hands and soles of feet.

How Do I Catch Scabies?

Scabies is transmitted through close skin to skin contact with someone who is infected. The mite tends to infect the fingers and wrists most commonly, so holding hands with an infected person is the most common way of being infected. The contact usually has to be for a reasonable length of time, so shaking hands with someone, or hugging them, is not likely to be a risk. Other risks include sexual intercourse or sharing a bed with someone is infected, or cuddling babies and children who are infected.

The mite cannot survive for very long away from the skin, so bedding, towels, clothing and furniture used by an infected person are very unlikely to lead to an infection unless you use them at the same time or just after that person.

Scabies in humans is not caught from pets or domestic animals. Whilst these pets do have mites sometimes, the mites are a different species to the one that causes scabies. The other species cannot survive for very long on humans, and so they cannot cause the symptoms associated with scabies.

Scabies is not associated with poor hygiene or unclean living conditions. It can affect anyone regardless of their age, race, gender or social class. Crowded living conditions, or institutions like nursing homes, can increase the risk of transmission, because it is more common for people to regularly be in close contact with each other. This makes it more likely that the mite can transfer from one person to another.

The symptoms of scabies only appear 2-6 weeks after you are infested, but it is possible to transmit the infection as soon as you catch it. This means people have a long period of time when they do not realise they have the disease. During this time infected people will probably not avoid direct contact with other people, or try to prevent themselves from transmitting it, because they do not know they have it. As a result, scabies infections can spread very quickly and very easily.

How Does The Doctor Diagnose Scabies?

It can be difficult for a doctor to diagnose scabies. Often the itchy rash can be confused for other skin conditions, such as eczema.

The only way to definitely confirm scabies is to see the mites or their eggs. The mites are not visible to the naked eye. A doctor might try and identify the burrows that the mite makes. To do this, the doctor rubs some ink over the itchy area, and then wipes it away with alcohol. If there are burrows present, some of the ink will run into them, and they will show up as dark lines on the skin. The doctor might then take a skin scraping of the area to try and find a mite.  A skin scraping test isn’t usually painful. The doctor may look at the skin scraping there and then, or he may send it to the laboratory. At the laboratory it will be looked at under a microscope, to see if they can identify any mites or eggs.

Although seeing the mites is the only way to be sure it is scabies, often a doctor does not look for the mites, or cannot find them in the sample. If the symptoms and rash suggest scabies, this will sometimes be enough for a doctor to make the diagnosis. Additionally, if you have had recent contact with someone who has scabies, or if a number of people in your house or family develop the rash at around the same time, this might help the doctor diagnose scabies.

What Is The Treatment For Scabies?

The most common treatment for scabies is an insecticide cream. In the United Kingdom, there are two creams, one known as permethrin cream, and one known as malathion cream. Treatment is also available in tablet form, but it has more side effects than the cream without being any more effective, and so it is not commonly used. If the doctor gives you treatment for scabies, they should also provide treatment for everyone in your house, and anyone that you have had sex, or other close physical contact with, in the previous six weeks. Everybody should be treated at the same time otherwise it is very easy for reinfection to keep occurring.

If you are embarrassed about contacting sexual partners, your G.P. surgery may be able to contact them for you, without giving them any information about you or your identity.

How Do I Apply the Treatment?

To apply the treatment, have a hot bath and then dry the skin. Apply the cream all over the body, starting from below the ears and chin. Make sure the cream is well applied under the fingernails and toenails, and in all the skin folds around the finger, toes, breasts and buttocks. Children, the elderly, and people with poor immune systems should also apply the cream on their face and scalp. The cream should be left on for 8 hours if it is permethrin, and 24 hours if it is malathion. If you wash an area in that time, for example, your hands, then you should reapply the cream straight after. Babies and young children should have mittens on, to prevent them licking their hands, and swallowing the cream. After 7 days you should re-apply the cream in exactly the same way. This makes sure that if any eggs have hatched since the first application, the new baby mites are killed by the second application. Babies and young children should

You should avoid having sex, or any form of close body contact, until everyone has completed their treatment. If you do not, there is a high chance that reinfection will occur.

If you are pregnant or breastfeeding, or the treatment is for a baby or child under 2 years old, then you should this discuss this with the GP or pharmacist who prescribes it.

What Are The Side Effects of Treatment?

Permethrin cream may cause some side effects, such as tingling, stinging, numbness or irritation. If these side effects do not go away, you should see your doctor or your pharmacist.

Malathion cream may cause some side effects such as skin irritation. If this gets worse or does not go away you should see your doctor or your pharmacist.

What If the Treatment Doesn’t Work?

If the treatment doesn’t work, there may be a few different reasons for this. It may be that not all of your contacts with the infection were treated at the same time, or the treatment was not applied properly. In this case, the doctor will prescribe the same treatment.

If everyone was treated correctly, the doctor will try again with a different type of cream, and again everyone else will have to be-treated. The doctor will also re-examine the skin to check for new burrows, and to consider other possible diagnoses.

What If I Am Still Itching?

Although the treatment kills the mites, particles of mite tissue may remain under the skin for a while after treatment. It is these particles that the body is allergic to, so itching will continue until our body gets rid of these remaining particles. This usually takes another 2 weeks after treatment and does not mean that the treatment has failed. If the itching is very severe, the doctor may be able to prescribe you some tablets or cream to help relieve the symptoms. It is not usually necessary to go back to the doctor for a follow up. If the symptoms haven’t gone within 3-6 weeks after the first application, you should, however, make another appointment to see your doctor.

What Should I Do About Infection Control?

On the same day that you start the treatment, you should wash towels, clothes and  bedding on at least 50°C (50 degrees Celsius) to kill any mites. Hot ironing, dry cleaning, or tumble drying on a hot cycle for 10-30 minutes can all be used to kill mites. If there are items that you cannot treat in this way, sealing them in plastic bags for at least 72 hours will kill the mites.

Pets, furniture and carpets do not need to be treated with fumigation. Children should stay off school until the first application is complete.  It is possible to return to school or work the day after the first treatment. However, you should inform a child’s school of their infection so that the school can take precautions.

What Are The Complications?

Crusted Scabies

Crusted scabies (sometimes called Norwegian scabies), is caused by the same mite that causes classical scabies, and is transmitted in the same ways. It is a more severe form of the disease that is associated with people who have a poor immune system. Lots of things can weaken the immune system, including being very young or very old. Certain medical conditions, such as HIV (Human Immunodeficiency Virus), can weaken the immune system, and certain medical treatments such as steroids and chemotherapy can also weaken the immune system.

In people with a healthy immune system, it is thought that the body’s own defences somehow limit the reproduction process in the mites. This is why a person only usually has between 10 and 15 mites when they have classical scabies.

If someone has a weak immune system this does not happen, and so they can become infected with a lot more mites. This can mean they have millions of mites on their body at any one time. This causes the skin to become crusted with thick warty patches which is why it is known as “Crusted Scabies”.

The much higher numbers of mites makes crusted scabies even more infectious than classical scabies. As a result, even very brief contact with an infected person, or their clothes or bedding, can still lead to infection. However, even if you catch the scabies mite from someone with crusted scabies, if your immune system is healthy, you will only develop the classical (normal) type of scabies.

People with crusted scabies might be treated in hospital, to try and control the spread of infection. Crusted scabies is treated in the same way as classical scabies, either with a cream or a tablet.

Secondary Infection

The itchiness associated with scabies can lead people to scratch so much that they break the skin surface. When this happens, it is possible for the skin to get another type of infection, caused by bacteria, such as the condition impetigo.  Secondary infection is more common in people with crusted scabies, because they are more likely to end up with areas of broken skin. If you develop a secondary infection, your doctor may have to prescribe antibiotics to treat it.

Other Skin Conditions

If you already suffer from a skin condition, such as psoriasis or eczema, scabies can sometimes make this worse. Usually, once the scabies has been treated, any other conditions will return to their normal state.

What Happens If I Suffer From Re-infection

If you get re-infected with scabies, your response will be a lot quicker the second time. This is because your immune system remembers how to react to the scabies infection from the last time you were infected. It usually only takes 48 hours from when you are infected for the symptoms to start. If it is definitely a new infection, and not a failure of the treatment for the first infection, you will usually be given the same treatment again.

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