Causes of Scabies
The condition is caused by an infestation of the *Sarcoptes scabiei* var. *hominis* mite, a microscopic eight-legged parasite. The female mite burrows just beneath the surface of the skin to create a tunnel where she deposits eggs. The eggs hatch, and the mite larvae work their way to the skin's surface, mature, and can spread to other areas of the skin or to other people. The intense itching and rash are caused by the body's allergic reaction to the mites, their eggs, and their waste. The infestation spreads primarily through prolonged, direct skin-to-skin contact with an infested person, such as holding hands or sexual contact. Less commonly, it can spread through sharing clothing, towels, or bedding used by an infested person, particularly in cases of crusted scabies where the mite burden is extremely high.

Risk Factors
Scabies can affect anyone, regardless of hygiene or income, but certain factors increase the risk of infestation. Living in crowded conditions is a primary risk factor, as close physical proximity facilitates the spread of mites. High-risk settings include nursing homes, extended-care facilities, prisons, and child care centers. People with weakened immune systems, such as those with HIV/AIDS, organ transplant recipients, or the elderly, are at higher risk for developing a more severe form called crusted (Norwegian) scabies. Sexual contact is also a common mode of transmission among adults.

Prevention Strategies
Primary prevention involves avoiding direct skin-to-skin contact with an infested person and not sharing personal items like clothing or linen. To prevent re-infestation or the spread of mites to others within a household, all bedding, towels, and clothing used by the infested person and their close contacts should be washed in hot water and dried on a hot cycle. Items that cannot be washed should be sealed in a plastic bag for at least 72 hours, as the mites cannot survive away from human skin for more than a few days. Routine screening is not typically performed, but prompt identification and treatment of cases in institutional settings are crucial to prevent outbreaks.

Signs and Symptoms
The most defining symptom of scabies is intense itching (pruritus), which is usually severe and worsens significantly at night. A skin rash appears, often resembling pimples, tiny blisters, or scales. In some cases, thin, irregular burrow tracks made by the mites are visible on the skin as grayish-white or skin-colored lines. The rash typically favors specific areas, including the spaces between fingers, the folds of the wrists, elbows, and knees, the waistline, the navel, the genital area, and the buttocks. In infants and young children, the infestation may also affect the palms, soles of the feet, head, neck, and face. Symptoms can take four to eight weeks to appear in a person who has never had scabies before, while those who have had it previously may develop symptoms within days.

Diagnostic Methods
Clinicians typically identify scabies by examining the skin for the characteristic rash and checking for the presence of burrows. To confirm the diagnosis, a doctor may perform a painless skin scraping, where a sample of skin is taken from a suspected burrow and examined under a microscope for mites, eggs, or fecal matter. An ink test may also be used, where ink is applied to the skin and wiped away to reveal burrow tracks. In many cases, the diagnosis is made based on the appearance of the skin and a history of intense itching, especially if close contacts have similar symptoms.

Differential Diagnosis
Scabies can mimic other skin conditions, leading to potential misdiagnosis. It is often confused with atopic dermatitis (eczema), contact dermatitis, insect bites, or impetigo. In children, it may be mistaken for chickenpox or viral exanthems. The key differentiator is often the presence of burrows and the disproportionate severity of the itch, particularly at night, as well as the involvement of specific body areas like the finger webs.

Medical Treatments
Scabies is treated with prescription medications known as scabicides, which kill the mites and their eggs. The most common treatment is a topical cream containing 5% permethrin, which is applied to the entire body from the neck down (and often the head in infants) and left on for 8 to 14 hours before washing off. Other topical options include sulfur ointment, crotamiton, or lindane lotion. For severe cases, crusted scabies, or when topical treatments fail, doctors may prescribe oral ivermectin. It is critical to follow the application instructions precisely to ensure effectiveness.

Management Strategy
Successful management requires treating the infested person and all household members and sexual partners simultaneously, even if they do not show symptoms, to prevent re-infestation. Environmental decontamination is also essential; all clothing, bedding, and towels used within the three days prior to treatment must be machine-washed in hot water and dried on high heat. Floors and furniture should be vacuumed. Relief from itching may not be immediate; antihistamines, hydrocortisone creams, or soothing lotions like calamine can be used to manage symptoms while the skin heals. The itch often persists for several weeks as the immune system continues to react to the dead mites.

When to Seek Medical Care
Patients should see a doctor if they have an unexplained rash or intense itching that disrupts sleep. Medical attention is also needed if the rash shows signs of secondary bacterial infection, such as increased redness, swelling, warmth, pus, or honey-colored crusts (impetigo). If symptoms persist or new burrows appear more than 2 to 4 weeks after treatment, a follow-up visit is necessary, as retreatment may be required.

Severity and Disease Course
For most healthy individuals, scabies is a moderate condition that causes significant discomfort and sleep disturbance but is not life-threatening. The infestation does not go away on its own and requires treatment. Without treatment, the condition can persist indefinitely. A severe form called crusted (Norwegian) scabies can occur in people with weakened immune systems, the elderly, or those with disabilities. This form involves thick crusts containing thousands to millions of mites and is highly contagious, though it may not always be itchy.

Complications
The most common complication is a secondary bacterial skin infection, such as impetigo, caused by scratching that breaks the skin barrier. This allows bacteria like *Staphylococcus aureus* or group A streptococci to enter. In some populations, particularly in tropical climates, untreated streptococcal skin infections secondary to scabies can lead to serious post-infection complications, including post-streptococcal glomerulonephritis (kidney inflammation) and rheumatic fever. However, in developed settings with prompt treatment, these severe systemic complications are rare.

Prognosis
The prognosis for scabies is excellent. The infestation is curable with appropriate medication. While the itching (post-scabetic pruritus) can last for 2 to 4 weeks after the mites are killed, it typically resolves over time. Recurrence is common only if close contacts are not treated simultaneously or if proper cleaning measures are not followed, leading to re-exposure.

Impact on Daily Activities
The intense itching of scabies can severely impact quality of life, leading to sleep deprivation, fatigue, and difficulty concentrating at work or school. Children generally need to stay home from school or childcare until treatment has been completed (usually 24 hours after the first application). There is often a social stigma associated with the condition, which can cause anxiety, embarrassment, or isolation. Managing the laundry and cleaning requirements during treatment can also be physically and time-consuming for households.

Questions to Ask Your Healthcare Provider

• What specific medication is best for me or my child, and exactly how should I apply it?
• Do I need to treat everyone in my house, even if they aren't scratching?
• When is it safe for me to return to work or for my child to return to school?
• How should I clean items that cannot be washed, like coats or couch cushions?
• What should I do if the itching does not go away after treatment?
• What signs of infection should I look for in the scratched areas?

Q: Can I get scabies from my pets?
A: No, animals do not spread human scabies. Pets can be infested with a different type of mite that causes mange, which might cause temporary itching in humans but cannot survive or reproduce on human skin.

Q: Can I get scabies from a swimming pool?
A: It is very unlikely to get scabies from a swimming pool. Scabies is spread by prolonged skin-to-skin contact, and the mites are unlikely to survive long in the water or be transmitted without direct contact.

Q: Why am I still itching after I was treated?
A: Itching often continues for 2 to 4 weeks after successful treatment because your body is still having an allergic reaction to the dead mites and their waste left in the skin. This does not necessarily mean the treatment failed.

Q: How long do scabies mites live on furniture or clothes?
A: Scabies mites generally do not survive more than 2 to 3 days away from human skin. This is why bagging unwashable items for 72 hours is an effective way to decontaminate them.

Q: Is scabies a sign of poor hygiene?
A: No, scabies can affect anyone regardless of their cleanliness. It is a common misconception that it only affects those with poor hygiene; it is simply passed through contact.