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Scabies has played an important role in world history, with epidemics partially coinciding with military activities and major social upheavals. Scabies has been recognized as a disease for approximately 2500 years. Historically, it was treated with topical sulfur, a treatment still in use today.

Like syphilis, scabies has come to be known as the great imitator. Its spectrum of clinical manifestations may lead the practitioner to the wrong diagnosis.

The phrase "7-year itch" was first used with reference to persistent, undiagnosed infestations with scabies, not as a movie title.

Pathophysiology: The mite, S scabiei, spreads disease through direct and prolonged contact with the host. The mite remains viable for 2-5 days on inanimate objects; therefore, transmission through fomites, such as infected bedding or clothing, is possible, but less likely. Once bound to their host, 10-15 mites mate on the surface of the skin.

After mating, the male mite dies. The female mite burrows into the epidermis of the host using her jaws and front legs, where she lays up to 3 eggs per day for the duration of her 30- to 60-day lifetime. An affected host harbors approximately 11 adult female mites during a typical infestation. The eggs hatch in 3-4 days. The larvae leave the burrow to mature on the skin. Fewer than 10% of the eggs laid result in mature mites.

A delayed type IV hypersensitivity reaction to the mites, their eggs, or scybala (packets of feces) occurs approximately 30 days after infestation. This reaction is responsible for the intense pruritus, which is the hallmark of the disease. Individuals who are already sensitized from a prior infestation can develop symptoms within hours.

Scabies is usually transmitted by direct contact with an affected individual. Although disputed, some believe one can become infested by indirect contact with the personal items or clothing of an affected person because the mite can survive away from the skin for 2-5 days. This is much more likely to occur in the environment of someone with crusted or hyperkeratotic scabies.

In 1848, Norwegians Danielssen and Boeck described a highly contagious variant of scabies that occurs in immunocompromised patients. Crusted or hyperkeratotic scabies, as it has come to be known, is an overwhelming scabies infestation. This rare form of scabies occurs in elderly or mentally incompetent patients. Because of an impaired antibody response, these individuals can be infested with thousands to a couple million mites.

What is scabies?

Scabies is an infestation of the skin with the microscopic mite Sarcoptes scabei. Infestation is common, found worldwide, and affects people of all races and social classes. Scabies spreads rapidly under crowded conditions where there is frequent skin-to-skin contact between people, such as in hospitals, institutions, child-care facilities, and nursing homes.  However due to weakened immunity, elderly are more susceptible to scabies. 

The scabies mite

The mite is too small to be visible by naked eye. The female mite penetrates into the skin by its forelegs and mouth. It digs tunnels and lays down its eggs. The eggs hatch in 3 to 4 days. The mites mature in about 10 days, and then start to breed the next generation.

What are the signs and symptoms of scabies infestation?

Pimple-like irritations, burrows or rash of the skin, especially the flexural areas of wrists, elbows, or knee; the penis, breast, or shoulder blades, armpits, nipples, lower abdomen and external genitalia. The face and scalp of elderly are usually spared.

Rash develops at the point where the mite penetrates the skin. Thread like tunnel (usually less than 1 cm) can be seen as they dig tunnels under the skin.

If the infected person is allergic to the mite or its excreta, he or she may develop blisters.

The main symptom is intensive itchiness in the infected areas, which is more severe at night and after hot bath.  Sores on the body caused by scratching. These sores can sometimes become infected with bacteria.

How did I get scabies?

By direct, prolonged, skin-to-skin contact with a person already infested with scabies. Contact must be prolonged (a quick handshake or hug will usually not spread infestation). Infestation is easily spread to sexual partners and household members. Infestation may also occur by sharing clothing, towels, and bedding.

Who is at risk for severe infestation?

People with weakened immune systems and the elderly are at risk for a more severe form of scabies, called Norwegian or crusted scabies.

How long will mites live?

Once away from the human body, mites do not survive more than 48-72 hours. When living on a person, an adult female mite can live up to a month.

Did my pet spread scabies to me?

No. Pets become infested with a different kind of scabies mite. If your pet is infested with scabies, (also called mange) and they have close contact with you, the mite can get under your skin and cause itching and skin irritation. However, the mite dies in a couple of days and does not reproduce. The mites may cause you to itch for several days, but you do not need to be treated with special medication to kill the mites. Until your pet is successfully treated, mites can continue to burrow into your skin and cause you to have symptoms.

How soon after infestation will symptoms begin?

For a person who has never been infested with scabies, symptoms may take 4-6 weeks to begin. For a person who has had scabies, symptoms appear within several days. You do not become immune to an infestation.

When should I think about scabies?

  • Unexplained pruritus especially if other contacts are also itchy

  • `Atopic or irritant dermatitis' of very recent onset

  • Persistent insect bite reactions

  • Recurrent impetigo with itch

  • Pustular lesions on the palms and soles particularly in the young

  • Unusual urticaria

  • Unusual pruritic psoriasiform rashes that are crusted and scaling or blistering

How is scabies infestation diagnosed?

Diagnosis is most commonly made by looking at the burrows or rash. A skin scraping may be taken to look for mites, eggs, or mite fecal matter to confirm the diagnosis. If a skin scraping or biopsy is taken and returns negative, it is possible that you may still be infested.

Typically, there are fewer than 10 mites on the entire body of an infested person; this makes it easy for an infestation to be missed.


  • Major diagnostic criteria (presence of one confirms diagnosis)

    • ? Identifiable typical burrow particularly rash

    • ? Positive skin scrapings showing eggs or mite or

  • Minor criteria (two needed for likely diagnosis)

    • ? Typical itchy rash

    • ? Sudden onset of unexplainable itchy rash

    • ? Contact with a scabetic patient

    • ? Papules on penis

Who should be treated for scabies?

Anyone who is diagnosed with scabies, as well as his or her sexual partners and persons who have close, prolonged contact to the infested person should also be treated. If your health care provider has instructed family members to be treated, everyone should receive treatment at the same time to prevent reinfestation.

Can scabies be treated?

Yes. Several lotions are available to treat scabies. Always follow the directions provided by your physician or the directions on the package insert. Apply lotion to a clean body from the neck down to the toes and left overnight (8 hours).

After 8 hours, take a bath or shower to wash off the lotion. Put on clean clothes. All clothes, bedding, and towels used by the infested person 2 days before treatment should be washed in hot water; dry in a hot dryer.

A second treatment of the body with the same lotion may be necessary 7-10 days later.

Pregnant women and children are often treated with milder scabies medications.

General strategies in scabies management

An inviolable principle of scabies treatment is to treat all significant contacts. In practice this means all contact should have at least one treatment. Patients with definite or probable scabies should have two treatments. Caution should be exercised in treating infants, pregnant or lactating women, and the very elderly, as some preparations may be more toxic.

The treatment choice rests largely between topical permethrin or lindane applied to the skin.  Permethrin is preferred because of its apparent lesser toxicity. A large number of other agents may be used in special circumstances. The application must be done scrupulously. If one burrow is spared then the infestation will persist. The cream therefore needs to be massaged under nails and reapplied to any areas that are washed

  • Confirm the diagnosis preferably by identifying a typical burrow or positive skin scrapings.

  • Trace all contacts and ensure appropriate treatment.

  • Co-ordinate treatment.

    • Apply antiscabetic cream thoroughly. This usually means the entire body from the neck down. In some individuals the head must also be treated. Repeat in one week.

    • Treat all contaminated clothing and bedding. In some circumstances the immediate environment may also need decontamination.

    • Follow up 4-6 weeks later to ensure clearance.

Antiscabetic treatment




A synthetic pyrethroid which is probably the safest antiscabetic treatment. Proven effectiveness. Probably safe in infants, pregnant and lactating women, and the elderly.

Benzyl benzoate

This is often irritating. Toxicity is uncertain. It can be used as a spray for furnishings and the environment where there is heavy contamination.

Lindane(gamma benzene hexachloride)

The potential for neurotoxicity limits the use of this agent particularly in infants, pregnant and lactating women, and in the elderly.


Single dose may be effective. Simultaneous topical treatment is optional. Sometimes repeated doses are necessary. This drug is an important development in treating compromised patients, crusted Norwegian scabies, widespread unresponsive scabies and possibly some community epidemics in nursing home situations. Before prescribing, medical practitioners should be aware of the potential adverse effects and controversies in treating the young or the very elderly on multiple medications.

Miscellaneous other agents including maldison, and 6% precipitated sulphur cream

These agents require specialised experience and are not recommended as first line treatment. Some of these may also be used for spraying furniture

 Management of residents and staff for old age home

Staff should closely monitor the conditions of themselves and their residents. Immediate medical advice should be sought when a person have symptoms suggestive of scabies infection.

During a scabies outbreak, people who are in close contact with the patient, eg. roommates and staff, should apply the anti-scabies medication to prevent the spread of the disease.

Staff should wear gloves and apron when doing cleansing and taking care of the infected patient.

  • Management of the clothing and bed-linen

    • Patient’s clothing, bed-linen, pillowcase, etc., should be washed separately from those of their family members or other old age home residents.

    • Patient’s clothing, bed-linen, pillowcase, etc., must be boiled in hot water (60 ºC or above, for not less than 10 minutes) to get rid of the mite and their eggs. If boiling is not feasible, heating in a dryer (for not less than 30 minutes) or pressing with a hot iron are alternatives.

    • Place all non-washable personal items such as shoes, mattress, etc. in a plastic bag and seal them up for at least 14 days before they can be used as usual.
      Medical treatment

    • Effective medical treatment for scabies include anti-scabies agents (e.g. Benzyl Benzoate Emulsion) and drugs to control itchiness.

  • Method to apply Benzyl Benzoate Emulsion

    • In the evening after taking a bath, scrub and dry the body thoroughly. With the help of another person, use a brush to paint the emulsion from the neck downwards to cover the whole body (fingers webs and toe webs should be included, but not the head). Then put back the same clothes.

    • On the next morning, repeat the application without taking a bath. Then put back the same clothes.

    • On the next evening, take a hot bath and clean the whole body with soap and put on clean clothes afterwards.

    • In between the two applications of the emulsion, no need to change the clothing or bed linen.

    • Please note that two applications of the emulsion suffice to kill the mite. Over treatment gives rise to irritation and causes contact dermatitis. Re-apply the emulsion to the hands after washing since the previous coating has been removed by water.

    • After treatment, the itching may persist for one to two weeks. If the itchiness lasts for more than two weeks or if there are other changes in the skin, consult your doctor again.

How soon after treatment will I feel better?

Itching may continue for 2-3 weeks, and does not mean that you are still infested. Your health care provider my prescribe additional medication to relieve itching if it is severe. No new burrows or rashes should appear 24-48 hours after effective treatment.


Scabies is unlikely to cause a long-term disease state in healthy individuals. However, without adequate treatment, the lesions and associated pruritus may last for weeks to months.

Immunocompromised individuals are likely to develop crusted scabies, which may be impossible to fully eradicate.

Those infested may contract secondary bacterial infections via skin abrasion due to excessive scratching. These secondary infections may result in cellulitis, lymphangitis, and acute glomerulonephritis. Other than deaths related to secondary infection, scabies causes no appreciable mortality.

The above opinionated views and information serves to educated and informed consumer . The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. It should not replaced professional advise and consultation. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions

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