What is scabies?
Scabies is an itchy, highly contagious skin condition which is caused by an infestation by the itch mite Sarcoptes scabiei. This mite is so small it can only be seen with a magnifying glass or under a microscope. The mite cannot live more than three days without a human host, but it can survive up to a month when living on a human. The mite also lays eggs in human skin, which hatch and grow into adult mites. This means that symptoms of the condition can last for months or even years if not treated.
The rash caused by bites from the scabies mite is extremely itchy and is sometimes called “the seven-year itch.” The rash can be subtle, and sometimes scabies is hard to diagnose. The mite is spread from person to person by close contact. Animals can harbor a similar mite, but when the animal mite is passed to people, it cannot reproduce and dies within a few days.
Scabies affect everyone regardless of age, gender, race, social class, or personal-hygiene habits. However, a major risk factor is being a household member or sexual partner of an affected individual. Scabies is common in congested areas, such as nursing homes and hospitals and small congested homes, where it can spread widely. In people who have poor immune systems or who are malnourished, scabies can cause a syndrome called “crusted scabies” or “Norwegian scabies,” which causes skin thickening and a scaly rash.
Other conditions are sometimes confused with scabies. The scabies mite has no relation to body lice, although the treatment of the resulting skin disease is sometimes the same. Scabies is also different from bedbug bites. In contrast to scabies, bedbugs are visible to the naked eye and can live for long periods of time without feeding. Chiggers are a type of mite that can feed off human blood, but unlike scabies, they are acquired through contact with vegetation and feed for only a few days. Less commonly, the rashes of other skin diseases such as ringworm, shingles, eczema, allergic reactions (hives), or impetigo may be confused with that of scabies.
What is scabies mite? Life cycle of scabies mite:
Scabies is caused by an eight-legged mite (Sarcoptes scabiei var. hominis) that is less than 0.5 mm long. The life cycle of the scabies mite starts when the female tunnels (burrows) into the skin and lay her eggs. Larvae hatch from the eggs within three to 10 days and molt to become nymphs. Nymphs mature into adults that deposit additional eggs and live approximately for four weeks. Burrowing and movement of the mites cause intense itching due to a type of allergic reaction. If the person has never been exposed to scabies before, he or she may not show symptoms until four to six weeks after the initial infestation. Individuals who have been exposed in the past usually show symptoms earlier, that is, within a few days.
Where does scabies come from?
Scabies is almost always spread by protracted skin-to-skin contact with a person who carries the mite. The mites often begin to burrow at the site where they enter the body. Thus, skin transmission during sexual intercourse results in an infestation in the groin area.
It is important to point out that scabies is not always a sexually transmitted disease (STD) and can be acquired through casual contact. Less commonly, scabies infestation can happen through the sharing of clothes and bedding. Theoretically, you can get scabies from touching something that carries the mite, but that is not a major mode of transmission. The mite only lives for two to three days away from human skin. Scabies mites are not spread by contact with animals or pets.
What does scabies look like? What are scabies symptoms and signs?
Scabies produces a skin rash composed of small red bumps and blisters. It affects specific areas of the body. Scabies mainly 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, the sides and backs of the feet, the genital area, and the buttocks. The bumps (medically termed papules) may contain blood crusts. It is important to note that not every bump is a bug. 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. The skin may also be red or have sores due to scratching of the area. Open scabs or sores are susceptible to infection with bacteria.
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.
Textbook descriptions of scabies always mention “burrows” or “tunnels.” Burrows 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. Thus, scabies also should be considered whenever there is intense itching without an obvious rash, bite, or burrow. Often mistaken for burrows are linear scratch marks that are large and obvious and appear in people with any itchy skin condition. Scratching actually destroys burrows.
What does scabies feel like?
It is important to note that symptoms may not appear for up to two months after being infested 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. The itch of scabies is insidious and persistent. 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.
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 person in the middle of the night.
Symptoms occur from two to six weeks to appear after exposure. Symptoms include severe and continuous itching, especially at night. An indication that you may have scabies is if other members of your household are experiencing the same symptoms.
In crusted (Norwegian) scabies, the body is covered with a thick, dry, and scaly rash. The rash of crusted scabies may or may not itch, but it contains thousands to millions of mites. Crusted scabies is the most contagious form of scabies and the hardest to treat.
When to Seek Medical Care:
You should see a doctor if you suspect you have scabies. Many home remedies have been described, but most are untested. Plant extracts such as neem or tea tree oil have shown promise in small studies and deserve further investigation. Also, other conditions may cause rashes that itch, and it is important to have the correct diagnosis when considering treatment options. When calling to schedule an appointment, be sure to tell your doctor’s staff that you are concerned that you or your child may have scabies.
How is scabies diagnosed?
Most cases of scabies can be diagnosed by describing the symptoms to the doctor and by examination of the skin. There is no blood test for scabies.
- Sometimes, the doctor will do a skin scraping to make or confirm the diagnosis. This is performed by placing a drop of oil or saline on top of an affected area of skin. Then using a scalpel, the area is scraped, and the material that was collected is placed on a slide to examine under a microscope. The doctor will look for the mite or its eggs.
- The doctor may perform a felt-tip-marker test by drawing a washable felt-tip marker across the rash and then wiping it off with alcohol. This may help to identify a burrow because the ink penetrates deep into the skin.
- Often, there are very few mites that can be hard to find. Therefore, even if the scrapings are negative, the doctor may still recommend treatment if he or she is very suspicious that scabies is present.
Self-Care at Home:
Although you cannot cure a case of scabies without prescription medication from a doctor, there are certain things you can do at home to keep from reinfesting yourself or your family.
- Wash all clothing, towels, and bed linens that you have used in the last three days. Use hot water. You should use the dryer at high heat rather than air drying. Since the mites can survive on nonliving objects for several days, place the objects that are not machine washable (such as coats and stuffed toys) into a bag and store for a week.
- Use the medication as prescribed and instructed. Do not use it more than instructed because it can cause chemical irritation of your skin.
- Cut your nails, and clean under them thoroughly to remove any mites or eggs that may be present.
- Thoroughly vacuum your rugs, furniture, bedding, and car interior and throw the vacuum-cleaner bag away when finished.
- Try to avoid scratching. Keep any open sores clean to avoid super-added bacterial infection.
The first question affected people ask is how to get rid of scabies. The most commonly recommended treatment is a prescription cream which kills the mite. Anti-itch medications can help relieve symptoms while the cream is working.
- The treatment of choice medication is 5% permethrin cream (Elimite and others). The 5% cream is stronger than the over-the-counter permethrin, which is used for head lice and it will not cure scabies. ).
How to apply:
These creams are applied from the neck down, left on overnight, paying special attention to skin folds, the groin area, and the webs between fingers and toes. The cream should be applied to clean, dry skin. For best results, clip and clean all fingernails and toenails. Permethrin is usually left on the skin for 10-14 hours and then washed off in the shower. It is best to apply permethrin at bedtime and then wash it off in the morning. This application is usually repeated in seven days. Permethrin is generally safe for use in children older than 2 months of age.
- Do not apply to eyes, face, or mucous membranes.
- Discuss treatment with your doctor if you are pregnant ,breast feeding, or you are treating your newborn or a toddler.
Other common prescription agents for scabies
- An alternative treatment is 1 ounce of a 1% lotion or 30 grams of cream of lindane, applied from the neck down and washed off after approximately eight hours. Since lindane can cause seizures when it is absorbed through the skin, it should not be used if skin is significantly irritated or wet, such as with extensive skin disease, rash, or after a bath. As an additional precaution, lindane should not be used in pregnant or nursing women, the elderly, people with skin sores at the site of the application, children younger than 2 years of age, or people who weigh less than 110 pounds. Lindane is not a first-line treatment and is only recommended if patients cannot tolerate other therapies or if other therapies have not been effective.
- There is a prescription pill called Ivermectin (Stromectol) that has been used to treat scabies, but it is not FDA-approved for this indication. Because permethrin cream is relatively safe and effective, the pill is not usually needed. . 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 application of the cream, Ivermectin has a greater risk of toxic side effects than permethrin and has not been shown to be 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 a 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.
- All household members, sexual partners, and other close contacts should be treated at the same time regardless of whether or not they have symptoms. Anyone who has had skin-to-skin contact within the past month should be treated. If a child with scabies attends day care or a person is living in a nursing home or prison, then staff and others in close contact with the person should be treated. It is best to treat everyone simultaneously to minimize the risk that untreated people will reinfest treated people.
- Occasionally, the scratched skin may become infected, and sores may contain pus or become red and warm. This is a separate condition from scabies and is usually a bacterial infection. If this occurs, it is treated with an oral antibiotic or an antibiotic ointment applied to the area.
- Sulfur in petrolatum 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 in pregnant women and infants. They should not be used if patient is allergic to sulfa.
- The itching and rash may last for up to two weeks after treatment. If the symptoms last longer, it is possible that the person has been reinfested or that the cream was not used appropriately. In some cases, the treatment is repeated after two weeks if symptoms does not resolve. A second course of treatment and reassessment by the doctor is required in this setting.
- Itching can be control with antihistamine medications such as diphenhydramine (Benadryl), hydroxyzine (Atarax), cetirizine (Zyrtec), and promethazine (Phenergan). Sometimes, a short course of topical or oral steroids is prescribed to help control the itching.
It is difficult to prevent scabies. If a person is known to have scabies, they should not have close skin-to-skin contact with others until they have been treated. If one member of a household has scabies, all other household members, sexual partners, and close contacts should be treated simultaneously. Clothing, towels, and bedding from an affected person should be washed in hot water and dried in a dryer. If an article cannot be washed this way, it can be stored away from human contact for three days to eliminate mites.
In the hospital, staff should use gloves and gowns when treating patients who have a suspicious rash and itching.
Once properly diagnosed, treatment is generally very effective at curing scabies.
Are cases of scabies often misdiagnosed?
Scabies is very easy to misdiagnose because 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. Over a few weeks, however, mistakes like this become evident as patients feel worse and worse with symptoms they can’t ignore.
What are possible 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.
In what special situations can scabies be more easily spread?
Elderly and weakened people in nursing homes and similar institutional settings may harbor scabies without showing significant itching or visible signs. In such cases, there can be widespread epidemics among patients and health-care workers. Such cases are fortunately, uncommon.
What is Norwegian or crusted scabies?
Norwegian scabies, or crusted scabies, is a severe form of scabies first described in Norway. 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 in patients with AIDS, lymphoma, or other 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 the 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. Crusted scabies is hard to treat and may require several applications of lotions, use of ivermectin pills, and extensive skin care to treat the crusted skin.
A particular danger of crusted scabies is that these lesions often predispose to the development of secondary infections, as with staphylococcus bacteria.