Scabies is a skin infestation caused by a tiny mite called Sarcoptes scabiei that burrows into the top layer of your skin, lays eggs, and triggers intense itching. It affects millions of people worldwide, spreads through prolonged skin-to-skin contact, and is treatable with topical or oral medications. The itch is often worse at night and can persist for weeks even after the mites are gone.
What Causes Scabies
The scabies mite is microscopic, too small to see with the naked eye. It goes through four life stages: egg, larva, nymph, and adult. Female mites burrow into the outermost layer of skin (but never deeper), where they lay eggs and remain fertile for the rest of their lives after a single mating. The mites feed on your skin and the surrounding fluid, and their presence, along with the waste they leave behind, triggers an immune reaction that causes the characteristic itch and rash.
Scabies mites depend entirely on a human host to survive. Off the body, they can live up to two to three days under normal conditions, though immature forms may survive up to nine days in cooler temperatures with high humidity. This is why scabies spreads primarily through direct contact rather than contaminated objects.
How Scabies Spreads
Transmission typically requires about 10 to 15 minutes of direct, prolonged skin-to-skin contact. This is why scabies commonly spreads between sexual partners, family members sharing a bed, or caregivers and the people they care for. A quick handshake or brief hug is generally not enough.
Spread through shared clothing, towels, or bedding is possible but less common with ordinary scabies since the mites don’t survive long away from the body. The exception is crusted scabies, a severe form where mite numbers are enormous, making indirect transmission far more likely.
What Scabies Feels Like
The hallmark symptom is intense itching, particularly at night. If you’ve never had scabies before, symptoms can take four to six weeks to appear after the initial infestation. During that entire time, you’re contagious even though you feel fine. If you’ve had scabies in the past, your immune system recognizes the mites faster, and itching can start within one to four days of re-exposure.
The rash appears as small red bumps, tiny blisters, or thin, irregular lines on the skin (these lines are the actual burrows). Common locations include between the fingers, on the wrists, elbows, armpits, waistline, buttocks, and genitals. In infants and young children, the rash can also appear on the scalp, face, palms, and soles of the feet.
Crusted Scabies: A Severe Form
Most people with scabies have only 10 to 15 mites on their entire body at any given time. Crusted scabies (sometimes called Norwegian scabies) is a different story: a single patient can harbor up to two million mites. The skin develops thick, grayish crusts that crumble easily, releasing mites into the environment and making this form extremely contagious.
Crusted scabies typically develops in people whose immune systems are compromised, including those living with HIV/AIDS, elderly individuals, and people with conditions that prevent them from scratching, such as spinal cord injuries, paralysis, or severe cognitive impairment. Paradoxically, itching with crusted scabies is often mild or completely absent, which can delay diagnosis.
How Scabies Is Diagnosed
Doctors often suspect scabies based on the pattern of itching and the appearance and location of the rash, but confirming it requires finding the mite, its eggs, or its waste. The most direct method is a skin scraping: a drop of mineral oil is placed on a suspicious bump, the skin is gently scraped, and the sample is examined under a microscope. The challenge is that with so few mites present in a typical case, scraping the right spot can be difficult.
A simpler screening tool is the burrow ink test. Ink from a fountain pen is rubbed over the skin, then wiped away with an alcohol swab. If a burrow is present, the ink seeps into the tunnel and reveals it as a wavy line. This test is quick, painless, and useful when screening many people, though it works best when performed by someone experienced in identifying the markings.
Dermoscopy, which uses a handheld magnifying device with a light, can also identify mites in the skin. A trained practitioner using this method achieves about 91% sensitivity and 85% specificity, meaning it catches most true cases and correctly rules out most non-cases. Accuracy drops somewhat with less experienced examiners.
Treatment
The most common treatment is a topical cream containing 5% permethrin, which kills the mites and their eggs. You apply a thin layer from the neck down to the soles of your feet, making sure to get into all skin folds: between fingers and toes, around the waist, and behind the knees. For infants and adults over 65, the cream should also be applied to the scalp, temples, and forehead. Leave it on for 8 to 14 hours, then wash it off. If live mites are still visible two weeks later, a second application is needed.
An oral option is also available and is taken as two doses, spaced one to two weeks apart, with food. This is particularly useful for people who can’t easily apply cream to their entire body, or for crusted scabies cases where topical treatment alone isn’t sufficient. The oral medication hasn’t been established as safe for pregnant women or young children under about 33 pounds.
Everyone living in the same household should be treated at the same time, even if they don’t have symptoms yet. Because of that long incubation period in first-time cases, someone can be carrying mites for weeks without knowing it.
Cleaning Your Home After Treatment
On the same day you start treatment, wash all bedding, clothing, and towels you’ve used in the previous three days. Use hot water and a hot dryer. Temperatures above 122°F (50°C) sustained for 10 minutes kill both mites and eggs. Items that can’t be washed should be sealed in a plastic bag for at least 72 hours, since mites can’t survive that long without a human host.
You don’t need to fumigate your house or deep-clean every surface. Vacuuming furniture and carpets in areas where infested individuals spent time is a reasonable precaution, but the mites’ inability to survive off the body for more than a few days limits the role of environmental decontamination.
Why Itching Continues After Treatment
One of the most frustrating aspects of scabies is that the itching doesn’t stop when the mites die. Your immune system continues reacting to the dead mites, eggs, and waste still embedded in the skin. In one study, post-treatment itching lasted a median of about 52 days, with some people experiencing it for over four months. This doesn’t necessarily mean the treatment failed.
Topical steroid creams are the most commonly used remedy for this lingering itch, prescribed in about 83% of cases in one clinical review. Antihistamines, gentle moisturizers, and in rare stubborn cases, light therapy have also been used. The key is distinguishing persistent itch from a true reinfestation. If new burrows appear or the rash spreads to new areas, you may need retreatment.
Complications From Untreated Scabies
The biggest risk of untreated scabies isn’t the mites themselves but the scratching they provoke. Broken skin from constant scratching creates entry points for bacteria, leading to secondary infections like impetigo (a superficial skin infection with crusting sores) or cellulitis (a deeper, spreading infection). These bacterial infections can occasionally progress to more serious problems, including bloodstream infections, bone infections, and in some cases, chronic kidney or heart disease. Children and people in crowded living conditions are especially vulnerable to these cascading complications.