Scabies: What Causes It, How to Recognize Night Itching, and How a Dermatologist Treats It for the Whole Household

3 days ago

18 min read

Scabies is a skin disease caused by a mite called Sarcoptes scabiei var. hominis, about 0.3–0.4 millimeters in size, which burrows into the outer layer of the skin (epidermis) and lays eggs there. The hallmark symptom is severe itching that disturbs sleep, especially at night, together with small red bumps between the fingers, on the inner wrists, in the armpits, around the navel, along the waistband, and on the genitals. Several people in the same household often itch at the same time.

The reason scabies does not clear up is usually not that the medicine is too weak, but these three things: applying the medicine incompletely (forgetting under the nails, the buttock crease, behind the ears), not repeating the treatment on schedule, and treating only one person when the whole household is already infected. This article, written by a dermatologist, explains how to tell whether it is scabies, the actual medicines used with their strengths and number of days, how to apply them step by step, and why itching can continue for several weeks after all the mites are dead, which does not mean the treatment has failed.

What Is Scabies, and What Are the Mites Doing Under the Skin

A fertilized female scabies mite bores into the top layer of the skin and keeps tunneling at roughly 0.5–5 millimeters a day, laying 2–3 eggs a day along the way. The eggs hatch into larvae in 3–4 days and become adults within about 10–14 days. This cycle repeats until something stops it.

What causes the itching is not the mite walking around, but the body's allergic reaction to the mite, its eggs, and its droppings. This is why people with scabies for the first time may not itch during the first 2–6 weeks, since the body does not yet recognize the mite's proteins. But if someone who has had scabies before is infected again, the itching starts much sooner, within 1–4 days.

Another number worth knowing: in ordinary scabies in a person with a normal immune system, there are only about 10–15 mites on the body. This explains why skin scraping often misses the mites, and why the severity of itching does not depend on the number of mites at all.

What Causes Scabies: How It Is Actually Spread

Prolonged skin-to-skin contact is the main route. It takes continuous contact of roughly 10–20 minutes or more, such as sleeping in the same bed, holding a child, hugging, or holding hands for a long time. A quick handshake or sitting and chatting does not spread it.
Sexual intercourse counts as skin-to-skin contact that is long enough, so in adults scabies can be considered a sexually transmitted infection.
Recently used bedding and clothing. Mites that fall off the skin can live outside the human body for about 24–36 hours at room temperature, so they can spread through shared bed sheets, towels, and clothes, but this is a secondary route.
Crowded places. Dormitories, camps, prisons, shelters, and elder care facilities are where group outbreaks are seen most often.
It is not caused by being unclean. People who shower twice a day can still get scabies, and bathing more often does not remove mites living under the skin.

Animal scabies, such as mange in dogs, can pass to people, but this is a different species of mite that does not burrow or multiply on human skin. It causes a temporary itchy rash for about 1–2 weeks and then goes away on its own. It does not need to be treated like human scabies, but the pet does need treatment.

What Are the Symptoms of Scabies: What Scabies Itching Is Like

Intense itching at night that wakes you up. This is the most characteristic symptom. The higher skin temperature under the blanket stimulates the mites to move.
Small red bumps scattered over the skin, 1–3 millimeters in size, mixed with scratch marks, abrasions, and blood crusts.
Other people in the household itch at the same time. This clue carries about as much weight in diagnosis as the rash itself. If the whole household is itching, think of scabies first.
No rash on the face and scalp in adults. This is an important point that separates it from atopic dermatitis and contact dermatitis.
Antihistamines or steroids help for a while, then the itching comes back. This is because steroids suppress inflammation but do not kill the mites. Sometimes they change the look of the rash and make diagnosis harder, a condition called scabies incognito.

The Scabies Burrow: The Only Sign Visible to the Naked Eye That Confirms the Disease

A scabies burrow is a small straight or winding line, gray or skin-colored, about 2–10 millimeters long, often with a tiny dark dot at one end, which is the female mite. It is easiest to see on the webs between the fingers, the sides of the fingers, the inner wrists, and the outer elbows.

The trick is to look in very bright light, shine the light at an angle, and check where the skin is thinnest. Finding a real burrow is strong evidence, but not finding one does not mean it is not scabies, because scratching usually destroys the burrows before the patient reaches the doctor.

What Does the Scabies Rash Location Tell You: A Rash Map by Age

Adults: webs between the fingers, inner wrists, elbows, armpits, around the breasts, around the navel, waistband, hips, buttocks, male genitals, and webs between the toes.
Infants and children under 2 years: the rash can also appear on the palms, soles, scalp, and face. This is an important exception, which is why treatment in small children must include the head.
Older adults: the rash may be unclear and show up only as itching all over the body, so it is often misdiagnosed as age-related dry skin.

Ordinary Scabies in Adults (Classic scabies)

Appearance: small scattered red bumps with burrows between the fingers and on the wrists. Scratch marks stand out more than the rash itself.
Cause: about 10–15 Sarcoptes scabiei var. hominis mites, spread by prolonged skin-to-skin contact.
Severity/urgency: not an emergency, but treatment should start within a few days because it keeps spreading while you wait.
When to see a doctor: when night itching continues for more than 1–2 weeks, or when others in the household start to itch.

Scabies in Infants and Young Children (Infantile scabies)

Appearance: clear blisters and pustules on the palms and soles are more prominent than in adults, and the rash can appear on the scalp and face. Children are often fussy, cannot sleep, and scratch until wounds become infected.
Cause: spread from a caregiver who holds the child and sleeps with them, so almost every case has an adult in the household who is also affected.
Severity/urgency: needs prompt treatment, because the chance of secondary bacterial infection is high and the choice of medicines is more limited than in adults.
When to see a doctor: every case should be assessed by a doctor. Do not buy scabies medicine and apply it to a child under 2 months yourself.

Crusted Scabies (Crusted scabies / Norwegian scabies)

Appearance: thick, gray-yellow, bark-like scaly skin, usually on the hands, feet, elbows, knees, and scalp, with thick, misshapen nails, and it may itch only a little or not at all, which is a trap that delays diagnosis.
Cause: the mites can multiply to hundreds of thousands or millions. It is seen in people with weak immunity, people with HIV, people on long-term immunosuppressants or steroids, bedridden older adults, and people with neurological impairment who cannot feel itching.
Severity/urgency: urgent. It spreads very easily even with brief contact, is the source of outbreaks across whole hospital wards or care facilities, and carries a risk of bloodstream infection.
When to see a doctor: immediately. It must be treated with oral medicine together with several rounds of topical medicine under a doctor's care.

Genital Scabies and Sexually Transmitted Scabies

Appearance: firm, dark red raised bumps on the penis, scrotum, or groin. They itch a lot, and some bumps stay for a month even after treatment.
Cause: the same mite, spread by skin-to-skin contact during sex.
Severity/urgency: not acutely dangerous, but you should also be screened for other sexually transmitted infections, and sexual partners from the past 1–2 months must be treated at the same time.
When to see a doctor: when itchy bumps on the genitals last more than 2 weeks, or a sore does not heal. A doctor should tell it apart from syphilis, herpes, and molluscum contagiosum.

Scabies in Older Adults and Bedridden Patients

Appearance: often shows up as itching all over with an unclear rash, or as thick scales on the back and buttocks in bedridden patients.
Cause: dry, thin skin with age makes the rash look unlike the textbook picture, and living together in care facilities makes it spread easily.
Severity/urgency: the diagnosis should be confirmed quickly, because one missed case often turns into an outbreak across the whole ward.
When to see a doctor: when an older adult itches all over for no clear reason and moisturizer has not helped within 2 weeks.

Scabies Bumps That Have Not Gone Down After Treatment (Post-scabetic nodules)

Appearance: firm, dark red to brown raised bumps, 5–20 millimeters in size, in the armpits, groin, genitals, and around the navel. They itch from time to time.
Cause: an immune reaction to dead mite remains still in the skin. These are not living mites, so they are not contagious and do not need another round of scabies medicine.
Severity/urgency: not dangerous, but they can last for several weeks to several months.
When to see a doctor: when they interfere with daily life. The doctor may use a short course of high-potency steroid cream or inject steroid into the bumps, which helps well.

Which Conditions Look Like Scabies

Atopic dermatitis — chronic, comes and goes since childhood, appears in the skin folds, has no burrows, and others in the household do not itch along.
Chronic itchy bumps (prurigo) — distinct firm bumps on skin within reach of the hands, often following chronic itching from another cause.
Urticaria (hives) — raised red welts that move around and fade within 24 hours, while scabies rash stays in the same place.
Itchy rash from dry skin — itching all over, especially the shins, clearly better with moisturizer.
Impetigo — honey-colored crusts. It often occurs together with scabies from scratching and secondary infection, and both must be treated.
Head lice — itching mainly of the scalp, with eggs visible stuck to the hair. Unlike scabies, which does not affect the scalp in adults.
Drug rash — appears all over the body at once within a few days after starting a new medicine.

How Is Scabies Diagnosed

A doctor diagnoses scabies mainly from the history of symptoms + the location of the rash + others close to you itching at the same time. Additional tests are used to confirm, not to rule it out.

Skin scraping examined under a microscope. The doctor scrapes a burrow, adds a drop of oil, and looks for mites, eggs, or droppings. Finding them confirms the diagnosis 100 percent, but not finding them does not rule out scabies, since there are only about a dozen mites on the body.
Skin examination with a dermatoscope (dermoscopy). The doctor looks for a picture like a delta-wing glider at the end of the burrow. It is quick and painless.
Burrow ink test. Ink is applied to the skin and wiped off, and the ink stays in the burrow and shows as a line.
Treatment trial. When the clinical picture is very clear, the doctor may start treatment right away and reassess, which is an accepted approach.

What Are the Scabies Medicines: Names, Strengths, and the Actual Number of Days

Only a few mite-killing medicines are used in Thailand, and each has clearly different indications.

1. Permethrin 5% cream. This is the first-line medicine for adults and children from 2 months of age. Apply it over the whole body from the neck down, leave it on for 8–14 hours, then wash it off in the shower. Repeat once more on day 7. It is highly effective and the least irritating of this group. The sign that it has worked is that no new bumps appear after both rounds are completed.

2. Benzyl benzoate 25% lotion. This is a widely used option in Thailand because it is cheap and easy to find. Apply it over the whole body from the neck down, leave it on for 24 hours, then wash it off. It is usually repeated on 2–3 days in a row, or once more on day 7 as the doctor directs. Note that this medicine can sting and irritate the skin a lot, especially on the genitals and on skin broken by scratching. For children it must be diluted to 12.5% or 6.25% depending on age, and it should not be used in small infants without consulting a doctor.

3. Sulfur 5–10% in petrolatum ointment. Apply it over the whole body for 3 nights in a row, then wash it off. It is the safest option for infants under 2 months, pregnant women, and breastfeeding women. The downsides are the strong smell, the sticky mess on clothes, and dry skin.

4. Crotamiton 10%. It does not kill the mites as well as the first two, so it is not used as the main medicine, but it reduces itching, so doctors often use it as a supplement after the mites have been cleared.

5. Oral ivermectin. The dose is 200 micrograms per kilogram of body weight taken once, then repeated on day 7–14. It is used when applying medicine over the whole body is not feasible, such as bedridden patients, older adults who cannot take care of themselves, cases that did not clear with topical medicine, or when many people in a care facility must be treated at the same time. It is not used in children weighing under 15 kilograms and not used in pregnant women. It should be taken with food for better absorption.

6. Treatment of crusted scabies. It requires several doses of oral ivermectin (a commonly used schedule is days 1, 2, 8, 9, and 15) together with permethrin over the whole body almost daily in the early period, plus a scale-softening agent such as 5–10% salicylic acid cream or urea so the medicine can pass through the thick scale to reach the mites.

All of the medicines above are listed by their generic names. The choice of type, strength, and number of rounds must be assessed and prescribed by a doctor, taking into account age, weight, pregnancy, underlying conditions, and the severity of the disease.

How to Apply Scabies Medicine Correctly: The Steps That Decide Whether It Clears

Bathe and dry the skin completely before applying. Do not scrub the skin hard, because it will make the medicine sting more.
Apply the medicine over the whole body from the neck down to the toes, every square inch, not just the spots with a rash, because mites are also in skin that still looks normal.
The spots people forget most often, which is why treatment fails, are under the fingernails and toenails (cut the nails short and use an old toothbrush to work the medicine in), and every web between the fingers, the navel, the buttock crease, the genitals, under the breasts, behind the ears, and the soles of the feet.
In children under 2 years, older adults, and people with weak immunity, the scalp, face, and ears must also be treated, avoiding the area around the eyes and the lips.
If you wash your hands during the day, apply the medicine to the hands again each time.
Leave the medicine on for the full time for its type, then wash it off in the shower. Put on a fresh set of clothes and bed sheets on the same day.
Apply the medicine to the whole household on the same night.

Why You Must Repeat the Medicine on Day 7 to 14

Every scabies medicine kills hatched mites well, but does not kill all the eggs. The eggs that survive hatch into larvae within 3–4 days after the first application and can restart the cycle within two weeks.

Repeating on day 7 therefore catches the new generation of mites that have just hatched, while they are not yet old enough to lay the next generation of eggs. Repeating oral ivermectin on day 7–14 is for the same reason. Applying or taking the medicine only once is one of the leading reasons scabies comes back in weeks 3–4, even when the medicine used was correct.

Treat the Whole Household at the Same Time, and Handle Clothing and Bedding

Treat everyone living in the same home and sexual partners from the past 1–2 months, all on the same night, even if the person does not itch yet. Because the incubation period is long, 2–6 weeks, a person without symptoms may already be infected and will spread it back again.
Wash clothes, towels, bed sheets, pillowcases, and blankets used in the 3 days before treatment in water at 60 degrees Celsius or higher, or dry them in a hot dryer for 10–20 minutes.
Items that cannot be washed in hot water, such as body pillows, stuffed toys, shoes, and robes, should be sealed in a plastic bag and left for 72 hours. The mites will die on their own because they cannot survive more than 24–36 hours off human skin.
Vacuum the mattress, sofa, and car seats once. That is enough. There is no need to spray insecticide in the house, and you should not, because it does no good and is harmful to people in the home.
There is no need to throw away furniture or mattresses. The scabies outbreak is not in the house, but on the bodies of people who have not been treated.

Still Itching After Treatment: Itching After Treatment Is Not Treatment Failure

This is the issue that worries patients and makes them buy medicine and reapply it on their own more than any other. The truth is that scabies itching can continue for another 2–4 weeks, and in some people up to 6 weeks, after all the mites are dead. It is called post-scabetic itch, because the itching comes from an allergic reaction to the dead mites and droppings still in the skin, which the body needs time to clear on its own.

The signs that it is truly healing are that no new bumps appear, no new burrows appear, the itching gradually lessens week by week, and nobody else in the household itches more.

The signs that it has not truly cleared and you must go back to the doctor are that new bumps keep appearing after completing both rounds, new burrows are found, or the itching gets worse instead of lighter after 4 weeks.

While waiting for the itch to settle, doctors usually give oral antihistamines, a short course of low to medium potency steroid cream, and moisturizer applied often. Do not reapply scabies medicine on your own beyond what the doctor prescribed, because repeated permethrin or benzyl benzoate causes irritant inflammation of the skin, which makes the itching worse and is mistaken for scabies that has not cleared.

Does Scabies Go Away on Its Own, and Is There Really Food You Must Avoid

Scabies does not go away on its own. The mites keep multiplying on human skin for as long as nothing kills them. Leaving it only makes the itching worse, leads to bacterial infection from scratching, and spreads it to the people around you. In children, kidney inflammation after a streptococcal infection from scratching has been reported as a complication.

As for the belief about "foods to avoid with scabies", such as eggs, fermented foods, or seafood, there is no medical evidence for it. Food does not make the mites increase or decrease. What you can actually control is to cut your nails short to reduce scratching wounds, bathe in warm rather than hot water because hot water makes itching worse, wear loose, breathable clothing, and complete every round of medicine.

Warning Signs: When to See a Dermatologist Promptly

Fever, chills, a swollen, red, warm rash, pus, or honey-colored crusts, which point to a secondary bacterial infection from scratching.
Skin that is thick and scaly like bark, especially in older adults or people with weak immunity, which fits crusted scabies that spreads very easily.
You have completed both rounds as the doctor prescribed and new bumps keep appearing.
Scabies in an infant under 2 months, a pregnant woman, or a breastfeeding woman, who need specially chosen medicine.
Itching so much that you cannot sleep for many nights in a row, affecting work and school.
Several people in the household or dormitory itch at the same time, so treatment for the whole group should be planned together.

Short Summary

Scabies is caused by Sarcoptes scabiei mites living in the skin. It is not caused by being unclean, and it does not go away on its own without mite-killing medicine.
The most characteristic symptom is intense itching at night, together with a rash between the fingers, on the wrists, in the armpits, around the navel, and on the genitals, and often others in the household itch at the same time.
The main medicine is permethrin 5% cream applied over the whole body and left on for 8–14 hours. Other options are benzyl benzoate 25%, sulfur ointment 5–10%, and oral ivermectin in cases where it is indicated.
You must repeat on day 7 and treat everyone in the household at the same time. These two things are the cause of treatment failure more than the type of medicine.
Itching for another 2–4 weeks after the mites are dead is normal. Look at new bumps, not at the itching, and do not reapply scabies medicine on your own.
What to do today: see a dermatologist to confirm the diagnosis and get medicine for the whole household, instead of buying medicine and applying it only on the person who itches.

Frequently Asked Questions About Scabies

How do I know if it is scabies?

Look at three things together. One is intense itching at night that wakes you up, unlike ordinary itchy rashes that itch about the same all day. Two is the location of the rash. Scabies likes the webs between the fingers, inner wrists, armpits, around the navel, waistband, and genitals, and in adults it does not appear on the face and scalp. Three is that others in the household or sexual partners itch at the same time, which carries a lot of weight. If all three are present, suspect scabies first. The clearest confirming evidence is the burrow, a small line 2–10 millimeters long between the fingers, but it is often erased by scratching. A definite diagnosis can be made by having a doctor scrape the skin for microscope examination or examine it with a dermatoscope.

Does scabies go away on its own?

It does not go away on its own. Scabies mites can live and multiply in human skin continuously for months to years as long as nothing kills them. The longer it is left, the worse the itching gets, scratching breaks the skin and causes secondary bacterial infection that turns into impetigo, and it keeps spreading to people in the household. In children, kidney inflammation after a streptococcal infection from scratching has been reported as a complication. What does go away on its own is a different matter, scabies from pets such as mange in dogs, where the mite is a different species that does not multiply on human skin, so it causes itching for 1–2 weeks and then goes away on its own, but the pet must be taken for treatment.

What causes scabies and how is it treated?

Scabies is caused by Sarcoptes scabiei var. hominis mites, 0.3–0.4 millimeters in size, spread by skin-to-skin contact of roughly 10–20 minutes or more, such as sleeping in the same bed, holding a child, or sexual intercourse. Treatment rests on three pillars that must all be done. One is the mite-killing medicine. The main one is permethrin 5% cream applied over the whole body from the neck down and left on for 8–14 hours. Other options are benzyl benzoate 25% lotion left on for 24 hours, sulfur ointment 5–10% applied for three nights in a row for infants and pregnant women, and oral ivermectin 200 micrograms per kilogram when applying medicine over the whole body is not feasible. Two is repeating on day 7 to kill mites that have just hatched from eggs. Three is treating everyone in the household on the same night, together with washing laundry at 60 degrees Celsius. The choice and dose of medicine must be assessed and prescribed by a doctor.

How long is a person with scabies contagious?

A person with scabies can spread it from the day they are infected, even before any itching starts, which is an important point, because with a first infection the incubation period is 2–6 weeks before the itching begins. That means in those weeks or so the patient has already passed it to people in the household without knowing. Someone who has had scabies before and is infected again will itch quickly, within 1–4 days. After starting treatment, a person is generally considered to stop being contagious within 24 hours after the first round of mite-killing medicine is applied correctly, so they can go back to school or work the next day, except in crusted scabies, which has huge numbers of mites and spreads very easily. In that case the patient must be isolated and treated in several rounds as the doctor directs.

Is scabies dangerous?

In healthy people, scabies is not life-threatening, but it is not a small matter either. The main problem is itching so severe that you cannot sleep for several weeks in a row, which clearly affects work and school. The real dangers come from three complications. One is secondary bacterial infection from scratching, which can turn into impetigo or cellulitis. Two is that in children, kidney inflammation after a streptococcal infection can follow. Three is crusted scabies in people with weak immunity, where the broken skin is an entry point for bacteria into the bloodstream, and which is the source of outbreaks across whole hospital wards. So it should be treated to completion from the start and not left alone.

What are the medicines for scabies?

There are only a few mite-killing medicines in actual use. The main one is permethrin 5% cream, usable from 2 months of age, applied over the whole body, left on for 8–14 hours, and repeated on day 7. The second is benzyl benzoate 25% lotion, which is cheap and easy to find in Thailand, left on for 24 hours, but it stings the skin a lot, especially on the genitals and broken skin, and must be diluted to 12.5% or 6.25% in children. The third is sulfur ointment 5–10% applied for three nights in a row, which is the safest option in infants under 2 months, pregnant women, and breastfeeding women. The fourth is crotamiton 10%, which does not kill mites very well but helps reduce itching. The last is oral ivermectin 200 micrograms per kilogram taken once and repeated on day 7–14, used in bedridden patients, cases that did not clear with topical medicine, or group outbreaks, and not used in children weighing under 15 kilograms or pregnant women. All of these are generic names. The choice and prescription must be made by a doctor.

Read more about other skin conditions in the collection of skin condition articles by a specialist doctor.

The information in this article is for education only and is not a diagnosis or a treatment order for any individual. The medicines mentioned are generic names for understanding. The choice of type and dose must be assessed and prescribed by a doctor only. Treatment results vary from person to person.

Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed September 23, 2026