Scabies: Infection, symptoms, treatment

Scabies is a contagious skin disease caused by mites. The infection usually occurs through close skin contact with the diseased. The parasites and their excretions trigger an allergic reaction with rashes and severe itching. However, scabies can be treated very effectively. Read here the most important information about the infection, symptoms and therapy of scabies.

Scabies: Brief overview

• Infection: over longer, intensive physical contact (hugging, sexual intercourse), sleeping together, caring for the sick, living together closely, sharing towels or clothing, playing together
• Symptoms: small pustules/bubbles, small, reddish-brown mite ducts on warm parts of the body (between fingers and toes, inner edges of feet, armpit area, around the areola, penis shaft, anal region), severe itching, burning (intensified at night) allergy-like skin rash.
• Treatment: externally applied insecticides (full body treatment), tablets
• Prognosis: usually very fast and reliable treatment success, but skin irritations may persist for a longer time. No immunity, repeated infections possible
• Obligation to report: to the public health department in case of infestation of several persons in community facilities (if a connection is likely)
• Important: Simultaneous treatment of all contact persons of the patient is necessary!

Where can you catch scabies?

Infectious diseases are contagious, and the same applies to scabies. “Infection” or “contagion” is sometimes referred to in connection with scabies as “infestation”, a term that describes a colonization of the body with parasites.

Scabies is transmitted through direct skin contact with sick persons. There is therefore usually no (animal) intermediate host, as is the case with many other parasitic diseases. For transmission, there must also be prolonged physical contact so that the mites can migrate from one host to the next. This is the case, for example, during sexual intercourse, which is why scabies is also counted among the sexually transmitted diseases.

Typical transmission paths are also, for example:

• sleeping in one bed together
• Personal hygiene of infants by their parents or of sick people by carers
• Hug and cuddle
• cooperative play

Contrary to widespread opinion, contaminated objects play a lesser role as a path of infection. This is because the mites lose their infectivity within a few hours at room temperature. Nevertheless, infection is possible, for example, via contaminated carpeting, shared bedding, clothing or towels. Also furniture or medical instruments with which the patient came into contact should always be cleaned.

Body hygiene plays only a minor role

What, according to recent studies, is far less important than expected is personal hygiene. This means that the risk of infection can hardly be reduced even with intensive personal hygiene. However, body care does play a role in the intensity of the development of scabies. Because the worse the personal hygiene, the more mites romp about on the skin.

Short touches, such as shaking hands, are usually not enough to infect yourself with scabies. Nevertheless, physical contact with infected persons without protective clothing should be avoided completely if possible.

Caution with the bark dross

The Scabies norvegica is a speciality. In this form of scabies, the affected persons suffer from a very dense mite infestation, mostly due to an immune deficiency. While patients with normal scabies rarely have more than 12 to 30 mite ducts at the same time, several million active animals may be present in bark scabies.

The more mites, the higher the risk of infection. Every flake of skin that a person with Scabies norvegica loses can be covered with several thousand mites. It is therefore all the more important to isolate the sick and to wear protective clothing when dealing with them and in their environment.

Incubation period of several weeks

In scabies, the incubation period can be several weeks: the typical scabies symptoms therefore only appear two to five weeks after the first infection. In the event of renewed infection, signs of disease appear after only a few days. Without therapy, scabies usually cannot be completely cured, although cases of spontaneous healing have been described.

Is scabies notifiable?

Scabies must be reported if it breaks out in communal facilities. These include, for example:

• Kindergartens
• Old people’s and children’s homes
• Schools
• Refugee accommodation, homes for asylum seekers

As soon as the management of the facility has knowledge of the scabies infestation, it must report it to the responsible health authority and also provide the personal data of the sick person. There is no basic obligation to report individual cases, but there is a duty to report two or more diseases with a suspected link.

Persons suffering from scabies are not allowed to work in community facilities or have contact with the people who are looked after there.

Scabies: Symptoms

Although scabies symptoms are typical, they are often not recognized and are often confused with allergies or other diseases.

A distinction is made between direct and indirect symptoms of scabies:

Direct scabies symptoms

The so-called mite ducts: The parasites dig small tunnels into the upper layer of skin, which can appear as irregularly winding (“comma-shaped”) mite ducts no longer than two to three centimeters long. When these are visible to the naked eye, they appear brownish-reddish.

Often, despite an infection, no corridors can be detected with the naked eye. For example, if they are covered by other skin phenomena, or the skin colour is very dark.

The number of mite ducts can vary depending on the stage of the disease. An otherwise healthy person normally has no more than eleven to twelve mite ducts, while the skin of immunocompromised patients can contain tens of thousands or even millions (scabies crustosa).

Even people with a healthy immune system can occasionally have several hundred mite ducts, usually about three to four months after infection. After a short time, however, the number of mite passages decreases strongly.

Personal hygiene has only a minor influence on the number of mites. Badly cared for people may have a few more mites in their skin.

Indirect scabies symptoms: The response of the human immune system to the mange mites is most of the trigger of the main symptoms. Itching is the classic scabies symptom, the scratching has given the disease its name:

• severe itching (pruritus) and/or slight burning of the skin
• Blisters and pustules, possibly also nodules. The vesicles are filled with liquid or pus, but do not contain mites. They can be available individually or in groups.
• Skin rashes (exanthema)
• Crusts (after the liquid-filled bubbles have burst open)

As with some other skin diseases, the itching of scabies is usually much stronger at night in a warm bed than during the day.

Where do the scabies symptoms appear?

The pregnant mite females drill passages into the skin to lay their eggs there. For this purpose, they prefer to seek out places where the skin is thin and particularly warm. These include:

• the areas between the fingers and toes (interdigital folds) and the inner edges of the foot
• the wrists
• the armpit regions
• the areolas and the navel
• the penis shaft and the area around the anus

The back is only rarely affected, head and neck are usually spared. In babies and toddlers, on the other hand, mite infestation can also occur on the face, the hairy head and the soles of the hands and feet.

The typical scabies symptoms are mainly seen where the mites sit. But they can also go beyond this and in some cases even affect the entire body. The latter applies especially to rashes (exanthema).

Special forms of scabies and their symptoms

Scabies can be divided into certain special forms, depending on the severity and type of symptoms:

• Scabies in newborns and infants
• well-kept scabies
• nodose scabies
• bullous scabies
• Scabies norvegica (crustosa), also called bark dross

In the context of some special forms of the disease, the scabies symptoms mentioned can vary or others can be added.

Cultivated Scabies

In patients who practice intensive body care including the use of cosmetics, the described skin changes often appear only very subtly, which can make diagnosis difficult. One then speaks of a cultivated Scabies.

Nodose and bullous scabies

The nodose scabies is characterized by the development of strongly itchy reddish-brownish nodules. These do not contain mites and sometimes persist for months after a successful killing of the parasites.

If particularly many smaller and larger blisters (vesiculae, bullae) form within the scabies, then we are talking about a bullous scabies. This form of progression is found more often in children.

Scabies norvegica (Scabies crustosa)

The bark dross (Scabies norvegica or S. crustosa) mentioned above differs significantly from the normal variant of dross due to the massive mite infestation. The skin reddens all over the body (erythroderma) and small and medium-sized scales are formed (psoriasiform picture).

Thick corneal layers (hyperkeratoses) develop on the palms of the hands and feet. Preferably on fingers, back of the hand, wrists and elbows, bark up to 15 millimetres thick can form. Under these crusts (which, by the way, are not caused by burst blisters) the skin appears red and moist and shiny. The bark is usually limited to a certain area, but can also spread towards the scalp, back, ears and soles of the feet.

It should be noted that the itching – the most typical of the scabies symptoms – can often be completely absent.

Scabies: Treatment

Scabies treatment is quick, painless and uncomplicated – at least in most cases. However, under certain circumstances, the treatment of the parasitic skin disease can cause difficulties, for example when several people within a community institution are affected. The condition of the patient’s immune system also plays a role, and there are variations in the treatment concept for some groups of patients.

The most important goal of scabies treatment is to kill the parasites that cause the disease. Various medications are available for this purpose, all of which, with one exception, are applied directly to the skin:

Permethrin: The insecticide is applied as a cream to the entire body surface and is considered the first choice. Only in exceptional cases does the doctor resort to alternatives.

Allethrin: Used in combination with piperonyl butoxide as a spray, but due to possible complications only used if permethrin therapy is not possible.

Benzyl benzoate: Although it is highly effective against mites, it is also used only in exceptional cases due to its relatively complicated application.

Ivermectin: Is also used as a worming agent and, unlike the other drugs used in the scabies treatment, is taken in tablet form.

Until a few years ago, lindane was also used more frequently as an alternative to permethrin, but in the meantime it has been largely abandoned, as this insecticide is quite toxic.

In developing countries, sulphur-containing preparations are increasingly used in dross treatment in addition to the inexpensive benzyl benzoate. In Germany, these no longer play a role due to the unpleasant smell during application and the possible toxicity.

According to studies, the common scabies treatment drugs only very rarely cause side effects such as rashes, diarrhoea and headaches.

Allethrin may cause serious respiratory complications in patients with pre-existing bronchial and pulmonary diseases and should therefore not be used in these individuals.

How the scabies treatment works

The above-mentioned active substances are aimed directly at the mites. Permethrin, allethrin and benzyl benzoate diffuse into the skin after application, spread there and kill the parasites. The exact application varies depending on the medication:

With permethrin, a single application is usually sufficient, whereby the entire body surface is to be treated with the cream. However, the mucous membranes and body orifices must be left out, as there are no mites in these areas and the body reacts much more sensitively to the active substance there. The head and thus also the facial skin are also not treated for these reasons. It is recommended to apply the permethrin cream in the evening and wash it off with soap the next morning (after 8 hours at the earliest).

If two weeks after the initial treatment there are still (or again) signs of active mite infestation, such as mite ducts or other typical skin changes, then the treatment must be repeated. This may also be necessary for people with weakened immune systems.

In otherwise healthy people without immunodeficiency, there is no risk of infection for others after the first proper scabies treatment. Children and adults can therefore go back to school or work after the first eight to twelve hours of therapy.

For allethrin and benzyl benzoate the application scheme is comparable. However, in some cases the active ingredient must be applied several times.

In the case of ivermectin, which is swallowed, the substance reaches the mites virtually “from inside”. Invermectin is swallowed as a tablet twice at eight-day intervals.

General measures for dross treatment

In addition to the actual therapy with the above mentioned drugs, there are some measures that support the scabies treatment and prevent further infections:

• The treating and contact personnel should wear gloves, in case of bark scabies (Scabies crustosa) also protective gowns.
• Both patients and staff should shorten their nails and brush the areas under their fingernails.
• The externally applied anti-mite agents work better if they are applied about 60 minutes after a full bath.
• The patient should wear cotton gloves during the exposure time and plastic gloves over it.
• After washing off the medication, completely fresh clothing should be put on.
• Close physical contact with sick people should be avoided.
• Intensive personal hygiene is important to prevent the mites from multiplying excessively.

In principle, all contact persons should be examined for symptoms of scabies and, if necessary, treated at the same time.

Clothing, bedding and other items with which the patient had prolonged physical contact should be washed at a minimum of 60° C.

If washing is not possible, it is sufficient to store the items in a dry place at least four days at room temperature (at least 20° C). (In cooler storage, the itch mites would retain their infectiousness for several weeks)

Special cases in dross treatment

Certain circumstances require a deviation from the usual scabies treatment, but the drugs used are usually the same.

Pregnant women, nursing mothers and children:

During pregnancy all available scabies medication is problematic. They should therefore only be used when absolutely necessary and even then only after the first third of the pregnancy.

The standard drug permethrin should not be used in pregnant women or only after prior consultation with a doctor. Although there is no indication of harmful effects, side effects and damage to the embryo/foetus cannot be excluded. Breastfeeding women should only use Permethrin under medical supervision and, as the active substance can pass into the breast milk, should take a break from breastfeeding for a few days. The dosage is reduced in these groups of patients so that less active substance enters the body’s circulation.

Newborns and infants under three years of age should also only be treated with (a reduced dose of) permethrin under strict medical supervision. The application scheme is similar to that for adults, although here the head is also treated, except for the areas around the mouth and eyes. The cream should also not be applied when the child has just been bathed, as the increased blood circulation in the skin could allow a critical amount of the active ingredient to be absorbed into the body through the skin.

As an alternative to permethirn, crotamiton is particularly suitable for children; otherwise this active substance plays a subordinate role in the treatment of scabies. Crotamiton is given to pregnant women only under great caution. Previously, benzyl benzoate was usually tried here.

Allethrin and Invermectin must not be used at all during pregnancy.

Pre-damage to the skin:

The skin is a natural barrier that prevents or hinders the penetration of external factors into the body. If the skin is damaged, for example by rashes or after severe scratching, not only pathogens but also externally applied drugs can enter the body more easily. The increased absorption of the substances can then lead to increased side effects.

In the case of larger skin defects, it is therefore important to treat them first, for example with corticosteroids (cortisol), before applying the scabies treatment medication. If this is not possible, systemic therapy with ivermectin must be used.

Scabies norvegica (S. crustosa):This special form of scabies causes extreme mite infestation, usually due to an immune deficiency. The number of mites here can be in the millions, and patients suffer from the formation of bark and thick layers of scales on the skin. It is therefore recommended to apply permethrin at least twice at intervals of ten to 14 days and to supplement the therapy with the intake of ivermectin.

In the preliminary stage, the thick layers of bark should be softened with special substances (e.g. creams containing urea) so that the active agent can be better absorbed into the skin (keratolysis).

A full bath before the scabies treatment, preferably with oil, supports the removal of the dandruff

Superinfections: Certain antibiotics are used to treat superinfections, i.e. in the case of infection with other pathogens (usually fungi or bacteria).

Dross treatment in community facilities

When scabies infections occur in communal facilities such as nursing homes or hospitals, often several patients are affected, and in unfavourable cases endemics may even occur (localised but unlimited occurrence of the disease). Scabies treatment is then often difficult. It must be carried out according to strict guidelines in order to be successful in the long term:

• All residents or patients of the facility as well as staff, relatives and other contact persons must be examined for possible infections.
• Patients with scabies must be isolated.
• All patients and persons who have had contact with infected persons must be treated simultaneously, even if no symptoms are visible.
• For infected persons, the scabies treatment must be repeated after one week.
• Bedding and underwear of all residents/patients must be changed and cleaned.
• Personnel and relatives must wear protective clothing.

Whereas in the past treatment in community facilities was mainly with permethrin, the trend is now moving more towards treatment with ivermectin. Observations have shown that mass therapy of all patients and contacts with a single dose of ivermectin has good chances of success and the relapse rates are the lowest. In addition, the administration of ivermectin is much less time-consuming than the application of external medications, which makes it easier to treat scabies with this active ingredient.

What are the complications?

In addition to the symptoms mentioned above, scabies can cause additional complications. One example are so-called superinfections. This is the name given to the additional infection with other pathogens in an already existing disease.

In scabies, for example, various bacteria can penetrate the skin more easily and cause infections (impetignation) because the upper layers of the skin are damaged by the constant scratching. The bacteria, mostly streptococci or staphylococci, cause in unfavorable cases:

• erysipelas: This inflammation of the skin, also called erysipelas, occurs within a sharply defined area of skin and is often accompanied by fever and chills.
• an inflammation of the lymph vessels (lymphangitis) and severe swelling of the lymph nodes (lymphadenopathy).
• rheumatic fever, sometimes also a certain form of nephritis (glomerulonephritis) These complications can occur a few weeks after infection with Group A Streptococcus, but are rare.

If bacteria enter the bloodstream, there is also a risk of blood poisoning.

Another possible complication of scabies is a skin rash (eczema) caused by anti-mite agents. The skin is reddened and usually also cracked, which in this case is no longer a result of the scabies, but is caused by the drying effect of the anti-mite remedies. The patients feel a slight burning and itching sensation.

Because certain nerve fibres are permanently activated by the constant itching during the ongoing disease, it is possible that nerve cells in the spinal cord are sensitised and reprogrammed. The nerves are now permanently irritated, so to speak, and report a persistent itching, even though there is no longer a trigger.

After a few months at the latest, however, the itching should subside along with the last of the scabies symptoms.

Risk factors

Within some groups, scabies occurs more frequently than in the general population. To be named:

• Children, as they have a lot of physical contact with each other and the child’s immune system is not yet as well developed as that of adults.
• Elderly people, especially if they already have pre-existing conditions and are placed in institutions. Their immune system is often weakened as well.
• People with reduced itching perception, such as those with Down’s syndrome (trisomy 21) and diabetics.
• Dementia can also promote scabies.

In addition, there are some diseases with which scabies occurs relatively often. Basically, a weakened immune system is a risk factor. Affected by this are, for example:

• Patients under chemotherapy
• HIV-positive
• Leukemia sufferers

Even a whole-body therapy with cortisol can increase the risk of scabies in unfavorable cases.

Hygiene plays only a minor role.

Occurrence of dross

In some regions in developing countries, up to 30 percent of the population is infected with scabies. In contrast, Scabies is now rather rare in the European Union, Britain and the United States, but outbreaks can occur again and again, mainly in communal facilities such as old people’s homes, day-care centres or hospitals. In unfavourable cases, endemics, i.e. chronic conditions, even develop here, whereby infections repeatedly occur within the limited area. Problem cases of this kind are then difficult and expensive to solve.

The total number of people infected with scabies worldwide is estimated to be around 300 million, although there are no data for individual countries, as, for example, individual cases do not have to be reported outside of Community bodies.

Description: Scabbers, what is it?

Scabies is a skin disease that has plagued mankind since time immemorial. The term comes from “scratching oneself” and thus already describes the problem: affected people experience an almost unbearable itching and therefore have to scratch themselves constantly.

Scabies belongs to the parasitic diseases (parasitoses), i.e. it is caused by microorganisms that need another organism to feed or reproduce.

The female itch mites reach a size of 0.3 to 0.5 millimetres and can therefore just be seen as a dot with the naked eye. The males on the other hand are smaller and no longer visible. A female will be about four to six weeks old and will lay up to four eggs daily from the second week of life.

Outside the host, for example on furniture, the mites can survive for a maximum of two days. Under unfavourable conditions (warm temperatures, low humidity) they die after a few hours.

Scabies: Examinations and diagnosis

Scabies is not always easy to detect despite its usually pronounced symptoms. The mite ducts, which can be up to a centimetre long and look like little commas, are often scratched up or covered by other skin symptoms. With darker skin types they are generally difficult or impossible to see.

If scabies is suspected, it must be confirmed by the detection of mites or their larvae or mite products. There are various diagnostic options for this:

Skin is often scraped off with a sharp spoon (curettage) to examine it microscopically. Ideally, the doctor should first open a mite duct for this. If he does not find one, he will at least select an area of skin where many symptoms are present.

A possible alternative to curettage can be top view microscopy. If a mite duct can be easily identified, the examiner can look at it with a special microscope or a high magnifying magnifying glass and possibly identify the mites directly.

More sensitive is the diagnosis with the dermatoscope. Here a brownish triangular shape, the head and the breast shield or the two front legs of the female mite are searched for.

Another method is the adhesive tape test or also Sellotape tearing. To do this, the doctor applies a transparent adhesive tape to the presumably affected areas of the body, pulls it off abruptly and then examines it under the microscope.

One of the oldest methods is the ink test (Burrow Ink Test). Where mite ducts are suspected, ink is dripped onto the skin and excess liquid is removed with an alcohol swab. In places where there are actually mite ducts, the ink penetrates and becomes an irregular black line. However, there are no scientifically founded statements about how specific or sensitive this method is.

Scabies: Course of disease and prognosis

With “normal” scabies you don’t need to go to hospital. Only in the case of severe encrustations due to a disease with Scabis crustosa or in the case of infants, toddlers or people in whom the immune system is suppressed (e.g. AIDS patients) may in-patient treatment in hospital be advisable.

Otherwise, however, with the right and consistent therapy the mites can be killed within a few days by means of cream or medication.

However, the symptoms of scabies, especially itching, may persist for several weeks. Especially when the skin of the affected person has been additionally damaged by dehydration and intensive scratching, the healing process often drags on.

Repeated infections with scabies are a problem, especially in community facilities. The strict treatment is an extremely time-consuming undertaking, as all patients as well as the close environment or all contact persons must be involved.