Scabies: Contagion, Symptoms, and Treatment

Scabies is a contagious skin disease caused by tiny parasites called scabies mites. The skin becomes inflamed and itchy. More about causes, symptoms and therapy

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In a nutshell: what is scabies?

Scabies (scabies) is a contagious skin condition caused by parasites. The tiny itch mites burrow into the upper horny layer of the skin and form small passages there.

  • Symptoms: Typical symptoms are severe itching and reddened, scaly skin that is partly covered with pinhead-sized nodules. On closer inspection, for example with a magnifying glass, the winding, elongated mite ducts can often be seen. The severe itching leads to frequent scratching - hence the name of the disease "scabies".
  • Diagnosis: The diagnosis of scabies is essentially based on the typical symptoms. Ideally, it is also possible to directly detect the itch mites, their eggs and feces.
  • Treatment: For the treatment of scabies, anti-mite agents are available that are applied to the affected areas of the skin in the form of ointments or creams. Treatment with tablets is also possible. In addition, the person concerned should remove the mites that may be in his clothing or bed linen. In most cases it is possible to kill all the itch mites and cure the disease. If left untreated, scabies can become chronic.

Symptoms of scabies

When do the first symptoms appear?

The classic symptoms of scabies do not appear the first time until two to six weeks after the parasite is transmitted. This is how long the immune system needs to develop a specific defense reaction against the mites. With further episodes of illness, it only takes a few days for symptoms to appear. Those affected can transmit scabies even before symptoms occur.

Which areas of skin are affected by scabies?

Itch mites prefer warm skin regions where the top layer of skin is particularly thin. The inflammatory changes in the skin therefore tend to occur between the fingers and toes, in the armpit area, in the area of ​​the navel or areola, on the ankles and inner edges of the foot as well as the genital region.

Usually the head, neck and back are not affected by the scabies. In babies and toddlers, scabies can also be found on the hairy scalp and the palms and feet.

The complexion of scabies can look very different - here is an example

© Shutterstock / Chuck Wagner

What are the typical symptoms of scabies?

Characteristic of scabies is the pronounced itching, which increases when it is warm.The skin is reddened on the affected areas and can burn easily. Pin-sized nodules form, and sometimes blisters in small children. Dandruff and crusts can develop, especially if there is additional scratching. However, the complexion of scabies can look very different. Sometimes the symptoms also deviate from the "classic pattern". In addition to the skin rash, if you look closely, you may see the mites' curved bores, sometimes even the itch mites themselves in the skin.

Since itching is generally promoted by warmth, the itching of scabies is particularly strong, especially at night, due to the warmth of the bed. The itching creates a vicious circle: Constant scratching damages the skin, which causes further itching.

Particularly contagious: scabies crustosa

In the case of a particularly serious form of scabies, the so-called bark scabies, the skin is changed over a large area beyond the typical regions. Large parts of the skin are reddened, the palms and feet are characterized by severe cornification and massive flaking. The otherwise prevalent itching is significantly less in bark scabies and can even be completely absent.

While most people with scabies have fewer than ten mites in the horny layer of their skin, there can be a few hundred in people with scabies. Therefore, this variant of the scabies is particularly contagious.

The mites dig into the upper horny layer of the skin and lay eggs there. It doesn't start to itch until weeks later

© W & B / Astrid Zacharias

Contagion: how is scabies transmitted?

Itch mites are mainly transmitted from person to person through skin contact. In order to become infected, however, the contact must take place for a sufficiently long period of time. Short touches - such as shaking hands - are usually not enough for infection with scabies. Frequently, the mites are transmitted through intensive physical contact to the partner or between parents and children.

Since itch mites can only survive for a relatively short time without their host, humans, transmission through blankets or clothing is possible, but less common. In this way, travelers get infected again and again when they spend the night in unkempt cheap accommodation. If there is insufficient personal hygiene, the number of mites on the skin is particularly high; this also increases the risk of transmitting the scabies.

Scabies is particularly widespread where many people live in a small space under poor hygienic conditions. There is also a particular risk of scabies if the immune system is weakened, for example in older people. But scabies also sometimes occurs in hospitals or nursing homes because of the close physical contact between the patient and the nursing staff.

How often scabies occurs depends on factors such as population density, medical care, people's health and hygienic conditions. However, itch mite infestation is not automatically proof of poor personal hygiene.

Diagnosis: how does the doctor recognize scabies?

The symptoms, the infestation of typical skin areas and the noticeable itching at night lead the suspicion in the direction of scabies. The diagnosis is all the more likely if members of the patient's family have similar symptoms.

The doctor makes the diagnosis by detecting the mites, their ducts, eggs, or excretions. With the dermatoscope (= incident light microscope), a magnifying glass-like device with integrated lighting, which he places on the skin, he may be able to recognize the itch mites.

In addition, the doctor can use a fine needle to pull material out of the passage and examine it under the microscope. With sufficient magnification, mites, eggs and ball of feces can be seen. In principle, direct evidence of scabies mites, alternatively eggs or mite faeces, is considered evidence of scabies.

However, it is often not possible to provide this proof: As a rule, there are no more than ten mites in the skin of an affected person. In addition, the mites and especially their eggs and their excretions are so tiny that they are often difficult to see even with the help of the reflected light microscope. Therefore, the diagnosis of scabies is usually made on the basis of the itchy skin changes in the typical areas.

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Therapy: what can be done about scabies?

The scabies can be treated with anti-mite agents (anti-scabies, acaricides or scabicides) for application or for ingestion.

Usually the scabies can be treated well. Several anti-mite agents are available for therapy. The goal is to kill any itch mites that are present in and on the skin. Since some preparations have strong side effects, the doctor carefully weighs up which medication to use. Particular caution is required, especially with pregnant women, breastfeeding women and children. Those affected should seek individual advice and follow the doctor's instructions exactly.

The active ingredient permethrin in the form of a cream is often used to treat scabies. The agent is applied over a large area according to the doctor's instructions and washed off thoroughly after a period of eight to twelve hours. If an unaffected person - for example the mother - applies the agent, they should use gloves. Patients should change their clothes and bed linen after treatment.

One therapy unit with the active ingredient is often sufficient. If after two weeks there are still signs of scabies, the doctor will advise you to repeat the application. Further medical check-ups usually take place up to four weeks after the start of therapy in order to rule out a flare-up of the disease.

Even if the mites have been successfully fought, itching and skin changes usually persist for a few weeks. The doctor then speaks of post-scabious eczema, i.e. inflammation of the skin that occurs as a result of the scabies. Even if all mites and mite eggs have been killed, components of the parasites can remain in the skin and maintain the inflammatory response of the body's own defense system. The doctor treats this skin irritation with anti-inflammatory ointments and creams. In addition, the person affected should regularly apply a moisturizing cream for a few weeks so that the skin recovers faster.

Permethrin is usually well tolerated as a treatment for scabies. However, it is poisonous in large quantities. So that the body does not absorb too much of the drug, it is advisable to rub the skin exactly as directed by a doctor. As far as possible, the agent should also not be applied to wounds. If in adults the more keratinized foot surfaces are also affected by the scabies, it can make sense to treat them beforehand with agents that soften the cornea - for example with salicylic acid. If the skin is severely inflamed by the scabies, the doctor can prescribe an anti-inflammatory, mostly cortisone-containing ointment before the actual treatment.

Because of the possible side effects, toddlers and infants should only be treated under strict medical supervision. As a precautionary measure, it is advisable not to give children a warm bath before applying the ointment. The warmth increases the blood supply to the skin, which means that larger amounts of the active ingredient can be absorbed.

Other active ingredients such as crotamiton or benzyl benzoate can also be used for the external treatment of scabies.

Therapy with tablets

Since May 2016, Ivermectin, a substance for the internal therapy of scabies, has been officially approved in Germany for the first time. Like the external treatment, the therapy with ivermectin tablets is carried out once. The dosage depends on the patient's body weight. If symptoms persist 14 days after ingestion, the treatment can be repeated.

Internal treatment with ivermectin can be advantageous in patients in whom external treatment of the scabies has already failed or does not promise much success from the outset. This is the case, for example, with people who are infected with hundreds of mites in the sense of a bark scabies. In the case of particularly severely affected patients, the doctor can even prescribe a combination of internal and external treatment. Internal therapy can also be appropriate if it is not guaranteed that the scabicidal cream can act on the skin for at least eight hours, or if the skin is already very irritated. Patients with scabies should discuss with their doctor which therapy is best for their individual case.

If the scabies occurs during pregnancy or breastfeeding, treatment is more difficult. In Germany, no drug against scabies has been officially approved for pregnant or breastfeeding women. The doctor therefore carefully weighs up in each individual case which medication to prescribe for the scabies.

Scabies: This is important in addition to therapy

In addition, drug therapy should be supplemented by general measures. In particular, items of laundry that come into intensive contact with the skin (bed linen, towels, underwear) are a potential source of infection. If you wash them at 60 ° C, all remaining scabies mites are usually killed. It is best to store textiles that must not be washed in an airtight plastic bag for four days at room temperature until the mites have died. These measures reduce the risk of re-infection if you come into contact with the textiles. Upholstered furniture is usually safe if it is vacuumed thoroughly and not used for four days.

Usually eight to twelve hours after the anti-mite agent has been applied, there is no longer any risk of infection. This means that after this time children can go back to kindergarten and school, adults can go back to work.

Possible complications

Scabies rarely lead to complications. In most cases, appropriate treatment can kill the itch mites. However, a weakened immune system increases the risk of complicated courses of scabies. In such cases it is important that the health status is closely monitored by the doctor. In severe cases, a sore rose (erysipelas) forms. If bacteria get into the bloodstream, in the worst case scenario blood poisoning (sepsis) can occur.

Background info: What are itch mites?

The causative agent of the scabies is the itch mite (Sarcoptes scabiei variatio hominis). This parasite specializes in humans. The itch mites, which belong to the arachnids, initially mate on the surface of the skin. The female itch mite - it is a tiny 0.4 millimeters in size - then digs passages into the top layer of skin, the horny layer. The mite lays its eggs in the corridors. But their waste products, small balls of feces, also remain there. The latter cause the immune system to react, causing the skin to become inflamed and itchy. After hatching, the larvae move to the surface of the skin and the life cycle of the itch mites begins again.

Can you prevent scabies?

The risk of scabies can be reduced by observing thorough personal hygiene, avoiding close physical contact with those affected and avoiding overnight stays in unkempt cheap accommodation when traveling. Sometimes it also makes sense to deal with close contact persons. It is best for the attending physician to decide whether this is advisable in individual cases.

Dr. med. Angela Unholzer

© W & B / private

Consulting expert

Dr. med. Angela Unholzer is a dermatologist with additional qualifications in allergology and dermatohistology. She completed her specialist training at the Dermatological University Clinic of the Ludwig Maximilians University in Munich and at the Clinic for Dermatology and Allergology at the Augsburg Clinic. At the latter clinic, she was senior physician in charge of the lighting department, the dermatological day clinic and the general dermatological outpatient department from 2006 to 2012. She then worked in a practice near Augsburg. She has had her own practice in Donauwörth since 2014.

Swell:

Guideline "Scabies, Diagnostics and Therapy" of the German Dermatological Society (DDG), as of 2016

Advice from the Robert Koch Institute: Scabies (scabies), https://www.rki.de/DE/Content/Infekt/EpidBull/Merkblaetter/Ratgeber_Skabies.html (accessed in March 2019)

BZgA: Scabies, https://www.infektionsschutz.de/erregersteckbriefe/kraetze-skabies/ (accessed in March 2019)

Important NOTE:

This article is for general guidance only and is not intended to be used for self-diagnosis or self-treatment. It cannot replace medical advice. Please understand that we do not answer individual questions.

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