Brief overview
- Symptoms: Small pustules/blisters, small, reddish-brown mite ducts on warm parts of the body (between fingers and toes, inner edges of feet, armpit area, around the nipple areolas, penis shaft, anal region), severe itching, burning (intensified at night) allergy-like skin rash
- Treatment: externally applied insecticides (whole body treatment), tablets if necessary
- Causes and risk factors: Spread of certain mites in the skin and a subsequent immune reaction; immunodeficiency and immunocompromising diseases increase the risk of disease; infection via prolonged, intensive physical contact
- Examinations and diagnosis: Microscopic examination of the skin, adhesive and rarely ink test
- Prognosis: Usually very fast and reliable treatment success, skin irritations may persist longer; no immunity, repeated infections possible
- Prevention: No preventive measures possible; simultaneous treatment of all contact persons of the infected person reduces the risk of infection
What is scabies?
Scabies is a skin disease that has plagued mankind since time immemorial. The term means “to scratch” and thus already describes the problem: those affected experience an almost unbearable itching and therefore scratch themselves constantly.
The female scabies mites reach a size of 0.3 to 0.5 millimeters 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 reaches an age of four to six weeks and lays up to four eggs a day from the second week of life.
Outside the host, for example on furniture, the mites survive for a maximum of two days. In unfavorable conditions (warm temperatures, low humidity) they die after just a few hours.
How does scabies manifest itself?
Although the symptoms of scabies are typical, those affected often do not recognize them and confuse them with allergies or other illnesses. This is partly due to the fact that scabies has been rather rare in recent years. However, it is now also on the rise again in the industrialized countries of the world.
Symptoms of the skin
The response of the human immune system to the scabies mites is usually the trigger for the main symptoms. Itching is the classic scabies symptom, and scratching has given the disease its name. The following symptoms mainly affect the skin:
- Severe itching (pruritus) and/or slight burning of the skin
- Blisters and pustules, possibly also nodules. The blisters are filled with fluid or pus, but do not contain mites. They occur singly or in groups.
- Crusts (after bursting of the fluid-filled vesicles)
As with some other skin diseases, the itching associated with scabies is usually much worse at night in a warm bed than during the day.
Mite tunnels
The parasites dig small tunnels into the upper layer of the skin, which appear as brownish-reddish or grayish-white, irregularly curved (“comma-shaped”) lines up to two to three centimeters long – the so-called mite ducts. They are usually visible to the naked eye.
Sometimes, despite an infection, no ducts can be seen with the naked eye. For example, if they are covered by other skin symptoms or the skin color is very dark.
The number of mite ducts varies depending on the stage of the disease. An otherwise healthy person normally has no more than eleven to twelve mite ducts, whereas the skin of immunocompromised patients sometimes contains tens of thousands or even millions (Scabies crustosa).
Even in people with a healthy immune system, there are sometimes several hundred mite galleries, usually around three to four months after infection. After a short time, however, the number of mite galleries decreases sharply.
Personal hygiene has only a minor influence on the number of mites. Poorly groomed people may have a few more mites on their skin.
Where do the symptoms of scabies appear?
- The areas between the fingers and toes (interdigital folds) and the inner edges of the feet
- The wrists
- The armpit regions
- The areolas and the navel
- The shaft of the penis and the area around the anus
The back is rarely affected, the head and neck are usually spared. In babies and small children, however, the mite infestation sometimes also occurs on the face, the hairy head and the soles of the hands and feet.
The typical scabies symptoms are mainly seen where the mites are located. However, they sometimes go beyond this and even affect the entire body. The latter applies above all to the skin rashes (exanthema).
Special forms of scabies and their symptoms
Depending on the severity and type of symptoms, scabies can be divided into certain special forms:
- Scabies in newborns and infants
- Cultivated scabies
- Nodular scabies
- Bullous scabies
- Scabies norvegica (crustosa), also known as bark scabies
In some special forms of the disease, the scabies symptoms mentioned vary or others are added.
Cultivated scabies
In those affected who practice intensive personal hygiene, including the use of cosmetics, the skin changes described above are often only very subtle, which makes diagnosis more difficult. Doctors then speak of a well-groomed scabies.
Nodular and bullous scabies
If a particularly large number of smaller and larger blisters (vesiculae, bullae) form as part of the scabies, this is referred to as bullous scabies. This form is more common in children.
Scabies norvegica (Scabies crustosa)
The above-mentioned bark scabies (Scabies norvegica or S. crustosa) differs significantly from the normal variant of scabies due to the massive mite infestation. There is reddening of the skin all over the body (erythroderma) and the formation of small and medium-sized scales (psoriasiform picture).
Thick corneal layers (hyperkeratosis) develop on the palms of the hands and feet. Preferably on the fingers, back of the hand, wrists and elbows, bark up to 15 millimeters thick forms. Under these crusts (which are not caused by burst blisters), the skin appears red and shiny and moist. The bark is usually limited to a specific area, but sometimes spreads to the scalp, back, ears and soles of the feet.
It should be noted that itching – the most typical scabies symptom – is often completely absent.
How is scabies treated?
The most important aim of scabies treatment is to kill the parasites that cause the disease. Various medications are available for this purpose, all of which must be applied directly to the skin, with one exception:
Permethrin: The insecticide is applied as a cream to the entire surface of the body. According to the guidelines, it is the drug of first choice. In cases where it is not effective or there are signs to the contrary, the doctor will use alternatives.
Crotamiton: The drug is applied to the skin as a lotion, cream, ointment or gel. It is used when treatment with permethrin, for example, is not possible.
Benzyl benzoate: The active ingredient is highly effective against mites and is considered the main drug for treating scabies alongside permethrin and crotamiton.
Allethrin: If treatment with permethrin is not possible or there are complications, doctors use the active ingredient in combination with piperonyl butoxide as a spray.
Ivermectin: In contrast to the other medications, this drug is taken in tablet form and is also used as an anthelmintic.
Until a few years ago, lindane was also frequently used as an alternative to permethrin, but doctors now largely avoid it as this insecticide is quite toxic.
According to studies, the drugs commonly used to treat scabies very rarely cause side effects such as skin rashes, diarrhea and headaches.
Allethrin may lead to serious respiratory complications in patients with pre-existing bronchial and pulmonary diseases and is therefore not usually suitable for treating scabies in these people.
How scabies treatment works
The active ingredients mentioned target the mites directly. Permethrin, crotamiton, benzyl benzoate and allethrin are absorbed into the skin after application, spread there and kill the parasites. The exact application varies depending on the medication:
In the case of permethrin, a single application is usually sufficient, whereby the entire body surface must be treated with the cream. However, mucous membranes and body orifices should be avoided, as there are no mites in these areas and the body reacts much more sensitively to the active ingredient there. The head and therefore also the facial skin should also be excluded from treatment for these reasons. Doctors recommend applying the permethrin cream in the evening and washing it off with soap the next morning (after eight hours at the earliest).
In otherwise healthy people without immunodeficiency, there is usually no risk of infection for others after the first proper scabies treatment. Children and adults are therefore allowed to go back to school or work after the first eight to twelve hours of treatment.
In Germany, a doctor must always confirm whether you can go back to work or whether affected children can go to school or nursery.
The application regimen for allethrin and benzyl benzoate is comparable. However, in some cases the active ingredient must be applied several times.
In the case of ivermectin, which is swallowed as a tablet, the substance reaches the mites “from the inside”, so to speak. Ivermectin is taken twice at eight-day intervals.
General measures for scabies treatment
In addition to the actual treatment with the medication mentioned, there are a number of measures that support scabies treatment and prevent further infections:
- The treating and other contact personnel wear gloves, in the case of bark scabies (Scabies crustosa) also protective gowns.
- Both patients and staff keep their nails short and brush the areas under the fingernails thoroughly.
- Topical anti-mite products work better if they are applied about 60 minutes after a full bath.
- After washing off the medication, put on completely fresh clothing.
- Avoid close physical contact with sick people.
- 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 treated at the same time if necessary.
Clothing, bed linen and other objects with which the patient has had prolonged physical contact should be washed at a temperature of at least 60 °C.
If washing is not possible, it is sufficient to store the items dry and at room temperature (at least 20 °C) for at least four days. If stored at a cooler temperature, the scabies mites would remain infectious for several weeks.
Scabies mites cannot be killed by hot bathing or in the sauna. These household remedies are not suitable for treating an itch infection, and hot bath water also carries the risk of burns.
Special cases of scabies treatment
Certain circumstances require a deviation from the usual scabies treatment, although the medication used is usually the same.
Pregnant women, nursing mothers and children
All available scabies medications are problematic during pregnancy. Doctors therefore only use them if absolutely necessary and even then only after the first trimester of pregnancy.
If breastfeeding women use permethrin – only under medical supervision – they should also take a break from breastfeeding for a few days, as the active ingredient may pass into breast milk. In these patient groups, the dosage is usually reduced so that less of the active substance enters the body’s circulation.
Newborns and small children under three years of age should also only be treated with (a reduced dose of) permethrin under strict medical supervision. The application scheme is the same as for adults, but the head should also be treated, with the exception of the areas around the mouth and eyes. Do not apply the cream if the child has just had a bath, as the increased blood flow to the skin may result in a critical amount of the active ingredient being absorbed into the body through the skin.
Crotamiton can be used as an alternative to permethrin, especially for children. Crotamiton is only given to pregnant women with great caution. Doctors usually try benzyl benzoate beforehand.
Allethrin and ivermectin are not approved for treatment during pregnancy.
Previous damage to the skin
In the case of larger skin defects, it is therefore important to treat them first, for example with corticosteroids (cortisol), before applying the medication for scabies treatment. If this is not possible, systemic therapy with ivermectin should be chosen.
Scabies norvegica (S. crustosa)
This special form of scabies is characterized by an extreme mite infestation, usually due to an immune deficiency. The number of mites can be in the millions and patients suffer from the formation of bark and thick layers of scales on the skin. Doctors therefore recommend using permethrin at least twice every ten to 14 days and supplementing the therapy with ivermectin.
It is advisable to soften the thick layers of bark in advance with special substances (e.g. creams containing urea) (keratolysis) so that the active ingredient is better absorbed into the skin. A warm bath before the scabies treatment, preferably with oil, helps to loosen the scales. However, make sure that the water is not too hot, otherwise there is a risk of scalding.
Superinfections
Certain antibiotics are used to treat superinfections, i.e. in the event of infection with other pathogens (usually fungi or bacteria).
Scabies treatment in communal facilities
- All residents or patients of the facility as well as staff, relatives and other contact persons must be tested for possible infections.
- Patients with scabies must be isolated.
- All patients and persons who have had contact with infected persons must be treated at the same time, even if no symptoms are visible.
- Scabies treatment must be repeated after one week for infected persons.
- Bed linen and underwear of all residents/patients must be changed and cleaned.
- Staff and relatives must wear protective clothing.
While doctors used to treat mainly with permethrin in community facilities, the trend is now moving more towards treatment with ivermectin. Observations have shown that mass treatment of all patients and contact persons with a single dose of ivermectin has a good chance of success and the relapse rates are the lowest.
In addition, taking ivermectin is much less time-consuming than applying topical medication, which is why scabies treatment with this active ingredient is easier to carry out.
What complications are there?
In addition to the symptoms mentioned, scabies sometimes causes additional complications. One example is so-called superinfections. This is the name given to the additional infection with other pathogens in an already existing disease.
- Erysipelas: This inflammation of the skin, also known as erysipelas, occurs within a sharply defined area of skin and is often accompanied by fever and chills.
- Inflammation of the lymph vessels (lymphangitis) and severe swelling of lymph nodes (lymphadenopathy)
- Rheumatic fever, sometimes also a certain form of kidney inflammation (glomerulonephritis). These complications usually occur a few weeks after infection with group A streptococci, but are generally rare.
If bacteria enter the bloodstream, there is also a risk of blood poisoning (sepsis).
Another possible complication of scabies is a skin rash (eczema) caused by anti-mite medication. The skin is reddened and usually cracked, which in this case is no longer a consequence of the scabies, but is caused by the drying effect of the anti-mite medication. Patients experience a slight burning and itching sensation.
Because certain nerve fibres are permanently activated by the constant itching during the ongoing disease, there may be a sensitization and reprogramming of nerve cells in the spinal cord. The nerves are now permanently stimulated, so to speak, and report a persistent itch, even though there is no longer any trigger.
How scabies develops
Scabies mites reproduce on the human skin. After mating, the males die while the females bore small tunnels into the outermost layer of skin (stratum corneum) with their powerful mouthparts. The mites remain in these tunnels for several weeks, lay their eggs in them and excrete many balls of excrement, which doctors also refer to as scybala. After a few days, the eggs hatch into larvae, which are sexually mature after a further two weeks. The cycle starts all over again.
The mites neither produce poison nor do they attack the body directly in any other way. The burrows they dig in the skin do not cause any pain or itching. The symptoms only occur because the body’s own immune system reacts to the mites and their waste products. The body activates certain cells and messenger substances that cause swelling, redness and itching. The affected areas of skin sometimes become inflamed and scratching further irritates the skin.
Because it takes a few weeks for the body to produce the special “anti-mite” immune cells after the first contact with the mites, the symptoms only appear after this period.
Risk factors
Scabies is more common in some groups than in the general population. These include:
- 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 live in care homes. Their immune system is also often weakened.
- People with reduced itch perception, such as those with Down’s syndrome (trisomy 21) and diabetics.
- Dementia also often favors scabies.
There are also some diseases with which scabies occurs relatively often. A weakened immune system is generally a risk factor. Affected by this are, for example
- Patients undergoing chemotherapy
- HIV-positive people
- Leukemia patients
Even whole-body therapy with cortisol increases the risk of scabies in unfavorable cases.
Hygiene plays only a minor role.
Where can you catch scabies?
Infectious diseases are contagious, and this also applies to scabies. In the case of scabies, doctors also speak of “infestation” in connection with “contagion” or “infection”, a term that describes a colonization of the body with parasites.
Typical transmission routes are, for example
- Sleeping together in the same bed
- Personal care of small children by parents or of sick people by caregivers
- Caressing and cuddling
- Playing together
Contrary to popular belief, contaminated objects play a lesser role as a route of infection. This is because mites lose their infectiousness within a few hours at room temperature. Nevertheless, infection is still possible via contaminated carpeting, shared bed linen, clothing or towels, for example. Furniture or medical instruments with which the patient has come into contact must also always be cleaned thoroughly.
Personal hygiene plays only a minor role
According to recent studies, however, personal hygiene is far less important than expected. The risk of infection can hardly be reduced even with intensive personal hygiene. However, personal hygiene does play a role in the severity of scabies. The poorer the personal hygiene, the more mites there are on the skin.
Brief contact, such as shaking hands, is generally not enough to become infected with scabies. Nevertheless, physical contact with infected persons without protective clothing should be avoided completely if possible.
Caution with bark scabies
The more mites, the higher the risk of infection. Each flake of skin shed by a person with Scabies norvegica is covered with up to several thousand mites. This makes it all the more important to isolate infected persons and to wear protective clothing when handling them and in their surroundings.
Incubation period of several weeks
The incubation period for scabies is usually several weeks: The typical scabies symptoms therefore only appear two to five weeks after the first infection. In the case of re-infection, however, signs of the disease appear after just a few days. Scabies cannot usually be completely cured without treatment, although cases of spontaneous healing have been described.
Is scabies notifiable?
According to the Infection Protection Act, 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 shelters, homes for asylum seekers
As soon as the management of the facility becomes aware of a scabies infestation, it must report this to the responsible health authority and also provide the personal details of the infected person(s). There is no general obligation to report individual cases, but there is if there are two or more cases with a suspected connection.
Occurrence of scabies
In some regions of developing countries, up to 30 percent of the population is infected with scabies. In Central Europe, on the other hand, scabies is less common; however, outbreaks do occur here too, mainly in communal facilities such as retirement homes, day care centers or hospitals.
In unfavorable cases, endemics, i.e. chronic conditions, even develop here, with repeated infections occurring within the limited area. Problem cases of this kind are then difficult and costly to deal with.
Doctors estimate the total number of people infected with scabies worldwide at around 300 million, although there is no data for individual countries as there is no mandatory reporting requirement everywhere, especially for individual cases outside of community facilities.
How is scabies diagnosed?
Scabies is not always easy to recognize despite its usually pronounced symptoms. The mite ducts, which are up to one centimeter long and look like small commas, are often scratched open or covered by other skin symptoms. They are generally difficult or impossible to see on darker skin types.
If scabies is suspected, it must be confirmed by detecting mites or their larvae or mite products. There are various diagnostic options for this:
A possible alternative to curettage is reflected light microscopy. If a mite duct is clearly visible, the doctor looks at it with a special microscope or a high magnification magnifying glass and may be able to recognize the mites directly.
Diagnosis with a dermatoscope is more sensitive. Here the doctor looks for a brownish triangular shape, the head and the chest shield or the front two legs of the female mite.
Another method is the adhesive tape test or tape tear. The doctor places a transparent adhesive tape firmly on the suspected infested areas of the body, pulls it off abruptly and then examines it under a microscope.
One of the oldest methods is the ink test (burrow ink test). Where the doctor suspects mite burrows, he drips ink onto the skin and removes the excess liquid with an alcohol swab. In places where mite burrows are actually present, the ink penetrates and becomes an irregular black line. However, there is no scientific evidence as to how specific or sensitive this method is.
How long does it take to heal?
Otherwise, however, with the right and consistent treatment, the mites can be killed within a few days using a cream or medication.
However, the symptoms of scabies, especially the itching, often persist for several weeks. The healing process is often protracted, especially if the affected person’s skin has suffered additional damage due to dehydration and intensive scratching.
Repeated scabies infections are a particular problem in communal facilities. Strict treatment is an extremely time-consuming undertaking, as all patients as well as the close environment or all contact persons should be involved.
Can scabies be prevented?
There are basically no measures that can reliably prevent an infection with scabies mites. However, it is important that all contact persons are also examined and treated in order to prevent the spread of the infection and reduce the risk of re-infection.
