Scabies

Medically Reviewed on 11/6/2023

What is scabies?

Scabies is an infestation of a highly contagious, microscopic skin parasite. Scabies are treated with scabicides that sometimes take more than one application to work. If itching and other symptoms continue more than four weeks after initial treatment, you should see a doctor.
Scabies is an infestation of a highly contagious, microscopic skin parasite.

Scabies is an itchy, highly contagious skin disease. Infestation occurs worldwide and can affect anyone of any age (including a baby or child) or race. It has been estimated that about 300 million cases occur each year throughout the world. Human scabies has been reported for over 2,500 years. Scabies have been reported to occur in epidemics in nursing homes, hospitals, long-term care facilities, and other institutions. In the U.S., scabies frequently affects the homeless population. It also occurs episodically in other populations of all socioeconomic groups, as well.

What is crusted scabies (or “Norwegian scabies”)?

Crusted scabies is a severe form of scabies first described in Norway. The outdated term “Norwegian scabies” is sometimes used, but it is inaccurate, since scabies is a worldwide problem.

Crusted scabies almost always affects people with a compromised immune system and is observed most frequently in the elderly, those who are mentally or physically disabled, and patients with AIDS, lymphoma, or other health conditions that decrease the effectiveness of the immune response. Due to the poor function of the immune system, an individual may become infested with hundreds of thousands of mites.

The lesions of this distinctive form of scabies are extensive and may spread all over the body. The elbows, knees, palms, scalp, and soles of the feet are most commonly the original sites of involvement, and the scaly areas eventually take on a wart-like appearance. The fingernails can be thickened and discolored. Interestingly, itching may be minimal or absent in this form of scabies.

A particular danger of crusted scabies is that these lesions often predispose to the development of secondary infections, as with Staphylococcus or Streptococcus bacteria, including impetigo, a common skin infection in children.

What are the types of scabies?

Some scabies infections can turn into crusted scabies in people with compromised immune systems. The difference between regular scabies and crusted scabies is the severity.

Symptoms of crusted scabies include:

  • Itching may seem absent or less prominent due to poor immune response, poor sensation, or inability to scratch
  • Thick, warty crusting of skin, especially between fingers and toes, elbows, and knees
  • Thickened nailbeds of fingernails or toenails
  • Larger numbers of mites and eggs

People with regular scabies may have 10-15 mites. People with crusted scabies can have thousands.

People with crusted scabies are incredibly contagious and need to receive immediate medical treatment.

What causes scabies?

Scabies is caused by an infestation by the itch mite Sarcoptes scabiei. Mites are small eight-legged parasites (in contrast to insects, which have six legs). They are tiny, just 1/3 millimeter long, and burrow into the skin to produce intense itching, which tends to be worse at night. The mites that infest humans are female and are 0.3 mm-0.4 mm long; the males are about half this size. Scabies mites can be seen with a magnifying glass or microscope. The scabies mites crawl but are unable to fly or jump. They are immobile at temperatures below 20 C, although they may survive for prolonged periods at these temperatures.

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Scabies See pictures of scabies as well as other bites and infestations See Images

Is scabies contagious?

Scabies is very contagious, and direct skin-to-skin contact is the mode of transmission. Scabies mites are very sensitive to their environment. They can only live outside a host body for 24-36 hours under most conditions.

  • Transmission of the mites involves close person-to-person contact of the skin-to-skin for 15-20 minutes, so risk factors include close contact with an infected person. It is hard, if not impossible, to catch scabies by shaking hands, hanging your coat next to someone who has it, or even sharing bedclothes that had mites in them the night before.
  • Sexual physical contact, however, can transmit the disease. In fact, sexual contact is the most common form of transmission among sexually active young people, and scabies has been considered by many to be a sexually transmitted disease (STD).
  • However, other forms of physical contact, such as a mother hugging a baby, are sufficient to spread the mites. Over time, close friends and relatives can contract it this way, too.
  • School settings typically do not provide the level of prolonged personal contact necessary for the transmission of the mites.
  • Crusted scabies is extremely contagious and may infect many contacts, including healthcare or institutional staff. Therefore, isolation from others and the use of protective gowns and gloves are required in healthcare settings until the infection is treated.

How does a person get scabies?

Scabies can infest any human who comes in contact with the mites, including people in good health. The only known risk factor is direct skin contact with someone who is infested. Good hygiene and health practices cannot prevent transmission if there is close contact with an infected person. The contact one experiences in social or school settings is not likely to be sufficient to transmit the mites. Sexual or other close contact (such as hugging) is required to spread the condition. The condition does appear in clusters, so outbreaks may occur within a given community.

Elderly and weakened people in nursing homes and similar institutional healthcare settings may harbor scabies without showing significant itching or visible signs. In such cases, there can be widespread epidemics among patients and healthcare workers. Such cases are dramatic but, fortunately, uncommon.

Can you catch scabies from a dog or cat?

Pets are infected by different types of mites than those that infect humans. Animals are not a source of the spread of human scabies. Scabies on dogs is called mange and is sometimes referred to as sarcoptic mange. When canine or feline mites land on human skin, they fail to thrive and produce only a mild itch that goes away on its own. This is unlike human scabies, which gets worse unless the condition is treated.

Who gets scabies?

Scabies spreads through close contact between people, especially through skin-to-skin contact, and can take as little as 15 to 20 minutes to be transmitted. Sexual partners, nursing home residents, and employees, children and workers at childcare facilities, and people living in close quarters are common examples of who gets scabies, but anyone can get it if they are exposed.

What are the symptoms of scabies?

Scabies produces a skin rash composed of small red bumps and blisters and affects specific areas of the body. The bumps (medically termed papules) may contain blood crusts. It is helpful to know that not every bump contains a mite. In most cases of scabies affecting otherwise healthy adults, there are no more than 10-15 live mites even if there are hundreds of bumps and pimples on the skin.

Textbook descriptions of scabies always mention "burrows" or "tunnels." These are tiny threadlike projections, ranging from 2 mm-15 mm long, which appear as thin gray, brown, or red lines in affected areas. The burrows can be very difficult to see. Often mistaken for burrows are linear scratch marks or welts that are large and dramatic and appear in people with any itchy skin condition. Scratching destroys burrows. Scratching may open the skin and lead to scab formation.

Where is scabies most common on the body?

Scabies may involve the webs between the fingers, the wrists, and the backs of the elbows, the knees, around the waist and umbilicus, the axillary folds, the areas around the nipples, and the sides and backs of the feet, the genital area, and the buttocks.

The scabies rash is often apparent on the head, face, neck, palms, and soles of the feet in infants and very young children but usually not in adults and older children.

How do you know if you have scabies?

It is important to note that symptoms may not appear for up to two months after being infected with the scabies mite. Even though symptoms do not occur, the infested person is still able to spread scabies during this time. When symptoms develop, itching is the most common symptom of scabies. Scabies does not cause pain. The itch of scabies is insidious and relentless and often worsens over weeks. The itch is typically worse at night. For the first weeks, the itch is subtle. It then gradually becomes more intense until, after a month or two, sleep becomes almost impossible due to the intensely itchy skin.

What makes the itch of scabies distinctive is its relentless quality, at least after several weeks. Other itchy skin conditions -- eczema, hives, and so forth -- tend to produce symptoms that wax and wane. These types of itch may keep people from falling asleep at night for a little while, but they rarely prevent sleep or awaken the sufferer in the middle of the night.

Should I see a doctor for scabies treatment?

If you or someone close to you has scabies, contact a physician for treatment and for advice about who else may benefit from treatment (for example, sexual partners or family members).

Patients with crusted scabies require isolation and/or barriers (gloves, gowns, for example) to protect others from the mites; such patients often are hospitalized and tested for underlying health problems (such as immunosuppression).

Which types of doctors diagnose and treat scabies?

Scabies is treated by several different healthcare professionals. The medical condition is commonly treated by primary-care doctors, including pediatricians, internal medicine specialists, and family medicine doctors. Many patients with skin symptoms seek treatment from a dermatologist or pediatric dermatologist. If crusted scabies is suspected, or if serious bacterial infection has set in, an infectious disease specialist may be consulted.

Sometimes, the condition may be first treated by an emergency medicine doctor if the patient seeks care in an emergency department.

What tests diagnose a scabies infestation?

Scabies is suggested by the presence of the typical rash and symptoms of unrelenting and worsening itch, particularly at night. Ultimately, the definitive medical diagnosis is made when evidence of mites is found from a skin scraping test. By scraping the skin (covered with a drop of mineral oil) sideways with a scalpel blade over an area of a burrow and examining the scrapings microscopically, it is possible to identify mites, eggs, or pellets (mite droppings). This process can be difficult, however, since burrows can be hard to identify.

Sometimes scratch marks are mistaken for burrows, and even the examination of scrapings from 15 or more burrows may only reveal one or two mites or eggs. If the characteristic physical findings are present, scabies can often be treated without performing the skin scrapings necessary to identify the mites. Polymerase chain reaction (PCR) testing is available to identify the genetic material of the scabies mites when the diagnosis is difficult, though this is not generally necessary. The mites can also be identified in skin biopsies that are performed when other causes of skin disease are suspected, again, usually not performed or necessary when the diagnosis of scabies is otherwise suspected.

Are cases of scabies often misdiagnosed?

Scabies is very easy to misdiagnose because an early subtle infestation may look like small pimples or mosquito bites. Those affected may believe they have another condition, such as bedbug bites or other kinds of rashes or infections. Over a few weeks, however, mistakes like this become evident as patients feel worse and worse with symptoms they can't ignore.

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What is the best treatment for scabies?

Curing scabies is rather easy with the administration of prescription scabicide drugs. There are no approved over-the-counter preparations that have been proven to be effective in eliminating scabies, and home remedies are not effective. Since scabies are a parasitic infestation, antibiotics used to treat bacterial infections are not effective.

The following steps may be included in the medical treatment of scabies:

  1. A mite-killer (scabicide) like 5% permethrin (Elimite) is the first-line treatment. Permethrin creams are applied from the neck down, left on overnight, then washed off. This application is usually repeated in one to two weeks. Permethrin is approved for use in people 2 months of age and older and is considered to be the safest and most effective treatment for scabies.
  2. Oral ivermectin (Stromectol) 200 mcg/kg is also an option, given once and then repeated in one to two weeks. It is well tolerated and may be the most practical approach to treating outbreaks in institutions. It is not a first-line treatment for those who are pregnant or nursing.

What OTC and prescription medications treat and get rid a scabies infestation?

There are no FDA-approved over-the-counter preparations that have been proven to be effective in eliminating scabies.

Prescription medications to treat scabies include:

  • Permethrin 5% cream (Elimite) is an insecticidal agent that is an effective scabicide in this concentration. It is applied from the neck down, left on overnight, and then washed off. This application is usually repeated in one to two weeks. Permethrin is approved for use in people 2 months of age and older and is considered to be the safest and most effective treatment for scabies.
  • Ivermectin (Stromectol), an oral antiparasitic medication that has also been shown to be an effective scabicide, although it is not FDA-approved for this use. The CDC recommends taking this drug at a dosage of 200 micrograms per kilogram body weight as a single dose, followed by a repeat dose two weeks later. Although taking a drug by mouth is more convenient than the application of the cream, oral ivermectin has a greater risk of toxic side effects than permethrin and is not superior to permethrin in eradicating scabies. It is typically used only when topical medications have failed or when the patient cannot tolerate them.
  • Crotamiton lotion 10% and cream 10% (Eurax, Crotan) is another drug that has been approved for the treatment of scabies in adults, but it is not approved for use in children. However, treatment failures have been documented with the use of crotamiton.
  • Sulfur in petrolatum (Sulfo-Lac, Sulfo-Lo) applied as a cream or ointment is one of the earliest known treatments for scabies. It has not been approved by the FDA for this use, and sulfur should only be used when permethrin, lindane, or ivermectin cannot be tolerated. However, sulfur is safe for use during pregnancy and in infants.
  • Lindane 1% lotion is a last resort due to adverse effects (seizures) and lack of safety in pregnant or nursing individuals, the elderly, and others.
  • In addition to scabicides, crusted scabies may also be treated with topical keratolytic creams to break down the skin crusts and allow scabicides to penetrate.

What home remedies get rid of scabies?

There are no home remedies to get rid of scabies, but important or helpful measures include:

  • Antihistamines, such as diphenhydramine (Benadryl), can be useful in helping provide relief from itching. Sometimes, a short course of topical or oral corticosteroid is prescribed to help control the itching.
  • Wash linens and bedclothes in hot water. Because mites don't live long away from the body, it is not necessary to dry-clean the whole wardrobe, spray furniture and rugs, and so forth.
  • Inform and treat sexual contacts or relevant family members (who either have symptoms or have the kind of relationship that makes transmission likely).

Just as the itch of scabies takes a while to reach a crescendo, it takes a few days to subside after treatment. After a week or two, relief is dramatic. If that doesn't happen, the diagnosis of scabies must be questioned.

Is it possible to cure scabies?

Scabies is curable with scabicide treatments. Treatment failures are not common but are possible, and people with crusted scabies may require a combination of different treatment methods.

What are the complications of scabies?

The intense itching of scabies leads to prolonged and often intense scratching of the skin. When the skin is broken or injured due to scratching, secondary bacterial infections of the skin can develop from bacteria normally present on the skin, such as Staphylococcus aureus or beta-hemolytic streptococci.

Is it possible to prevent a scabies infestation?

Avoiding close personal contact with infected people can prevent scabies. Sexual contacts and household members of people who develop scabies can be treated as soon as the condition is identified so that they will not develop the signs or symptoms of the condition. The treatment for these exposed people is the same as the treatment of the infected individual.

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Medically Reviewed on 11/6/2023
References
United States. Centers for Disease Control and Prevention (CDC). "Parasites - Scabies." Nov. 2, 2010. <http://www.cdc.gov/parasites/scabies/> Nov. 2, 2010.

American Academy of Dermatology. "Scabies." <https://www.aad.org/public/diseases/contagious-skin-diseases/scabies>.

Barry, Megan. "Scabies." Medscape.com. June 28, 2018. <http://emedicine.medscape.com/article/1109204-overview>.

American Academy of Dermatology Association: "SCABIES: DIAGNOSIS AND TREATMENT."

Centers for Disease Control and Prevention: "Scabies Frequently Asked Questions (FAQs)."

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National Center for Advancing Translational Studies: "Crusted scabies."

Johns Hopkins Medicine: "'Scratch' the Confusion Away: Hopkins Researchers."

National Center for Advancing Translational Sciences: "Crusted scabies."

Harvard Health Publishing: "Scabies."

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Cedars-Sinai: "Scabies."