"An eight-legged mite called a Sarcoptes scabie causes scabies in humans. The mite is not visible to the naked eye. These mites burrow into the upper layer of skin where they live and thrive. It’s believed that female mites lay 2-3 eggs per day. The presence of mites in the human skin results in small tunnel threadlike projections, which may appear as brown, red or grayish lines. Related symptoms include severe itching and rash. Itch often intensifies while in bed at night. The condition is spread through prolonged skin to skin contact such as in bed, or in settings such as schools or healthcare facilities. Symptoms appear up to 2 months after exposure.
Scabies can be difficult to diagnose and can be easily missed by a Dermatologist (The phrase "7-year itch" is based on an undiagnosed case of scabies). It requires examination of a skin sample under a microscope.Treatment options include prescription and over-the-counter medications. Once treatment begins the problem can be resolved in 2 to 3 weeks. Everyone in a family needs to be treated!
Prevention involves avoiding skin to skin contact, vacuuming, washing linen, washing or dry cleaning clothes and disinfecting the home or environment. Scabies are not spread by pets."
Scabies Causes, Diagnosis, Symptoms and Treatment
Dr. Chris Schach discusses human scabies causes, diagnosis and treatment options
What are scabies?
Scabies are caused by a human scabies mite that burrows under the outer skin layer. The mites lay eggs, increasing the size of the mite population under the skin. After a few weeks/months, the mites cause the skin to itch, and form blisters on the surface. Itch can cause eggs to get trapped under the nails, spreading the condition to other areas of the body.
What Causes Scabies?
What causes scabies is the parasite Sarcoptes scabiei which is attracted to the smell of human skin, human blood, and body heat. Scabies mites are about the size of a pinhead.
It is contagious as it can be quickly passed from one person to another through close physical contact and it may spread before or after symptoms appear. An individual may be infested by scabies through their family members, from nursing homes, classrooms and babies may catch the mites from daycare centers.
Because this condition can be passed from person to person, it is important to treat the entire family or the entire group in order to eliminate the scabies and stop the infestation. Eggs from the female usually mature within a few days, and new mites may spread through hugging, touching, sharing of clothes, sleeping on the same bed, and using other household and personal belongings of an infected person. It can also spread through sexual contact.
Animals are not a source of these types of mites and people are unlikely to contract this condition from infected animals such as dogs and cats
A specific mite only prefers one type of host so this type of mite from animals will not find the human skin as a favorable environment to multiply and thrive. Dog scabies on humans will cause mild skin irritation and only last for a few days. Pets cannot spread human mites.
How many mites are found on a patient?
Approximately 10 to 12 mites are found on each patient.
What is the lifespan of the Mite?
- Female: 4 to 6 weeks
- Lays 40 to 50 eggs
- Lays 3 eggs per day in a tunnel
- Eggs hatch in 4 days
- Mites burrow 2mm to 3mm per day
- When larvae hatch they migrate to the surface of the skin and then mature into adults
- Females and males copulate
- Females burrow, males fall off the skin
Who gets scabies?
Anyone can get scabies. Some people are more susceptible such as:
- People in hospitals
- Elderly and bedridden patients in nursing homes
- Adults who are sexually active
- Mothers with younger children
- Children (more common than adults, most common form is called nodular scabies, can be transmitted during play)(1)
How Long Can Scabies Mites Survive on Clothing?
Scabies mites can survive for 3 to 4 days on furniture, clothing, and bedding.
What Are Crusted Scabies?
There is a rare form of scabies called crusted scabies (also called Norwegian or hyperkeratotic scabies). People who have immune systems that are not working properly can contract this infection, enabling thousands or even greater than 1 million mites to burrow into the skin.
Crusted scabies is very contagious such a skin crust that contains a mite can be shed. This type of mite can live for a week without being burrowed into a human.
Crusted scabies requires a prescription medication that contains ivermectin. Doctors usually prescribe 2 doses, taken during two consecutive weeks.
Is Scabies Hereditary?
No. If many family members contract scabies, it is due to close contact.
What are Skin Diseases Confused With Scabies?
Misdiagnosis of scabies is common!(1) Be sure to tell your Dermatologist before you are diagnosed if intensely itching symptoms starts at night and possible sources of contact with an infected individual.
- Acute urticaria (usually itching papules)
- Eczema (skin inflammation)
- Papular dermatitis
- Irritant dermatitis
- Contact dermatitis
- Atopic dermatitis
- Dermatitus herpetiformis
- Fungal infections
- Insect bites
- Lupus (red or purple lesions)
- Mycosis fungoides
How Quickly Do Symptoms Appear?
Symptoms may appear within 6 weeks after being infected with the mite if you never had scabies before. However, it can still be transmitted to another person through close contact even though there appear to be no symptoms. Symptoms can appear in 1 to 4 days if a person had a prior problem.
Where do scabies look like on the skin?
A scabies rash can appear anywhere on the body. It is rare to see scabies infection above the neck.
Common areas of the body are:
- Skin areas that are usually covered with jewelry or clothing
Other common places include:
- Female breast areolae
- Male genitals
What is the most common symptom?
Intense itching is the most common symptom, gradually becoming more noticeable at night. It will get worse until the mites are eliminated. A person may experience an itchy skin rash that may appear as small red bumps, blisters or red sores. In some cases, burrow tracks or the appearance of black dots are evident.
The condition usually spreads to different areas of the body, such as the face, neck, hands, palms, buttocks, nipples and breasts, genitalia, armpits, elbows, waist and scalp. It is common to experience no itching on the neck and head (the one exception is scabies in babies).
Mainly occurs at night. Itching can be intense in body areas, and often avoids the neck and head. 50% of patients with crusted scabies do not suffer from skin itch.
Rash contains bumps and looks like it is in a line. Some people develop a rash that appears similar to eczema. It is possible to experience skin itch with no rash.
If the rash is tender it could indicate the presence of a bacterial infection.
Sores develop when skin is itched by the patient.
Results of crusted scabies where thousands of mites burrow into the skin. Rare condition in people with depressed immune systems.
What do scabies look like?
The scabies rash looks like a combination of red irritated skin and scratched skin. If the area becomes infected, then pus spots will develop. Even if you see the rash all over the body, the mites themselves are located primarily on the palms of the hands and in the spaces between the fingers. Areas, where the scabies mite is burrowing, will look like small lines along the skin that are grey in color.
To diagnose a rash caused by skin mites, doctors usually do a thorough examination of the patient’s skin. Doctors will look for signs of mite infestation, such as the appearance of rashes and burrows. Skin scrapings are taken from burrows for examination under a microscope in order to determine the presence of mites, eggs, or feces. In some cases, a drop of liquid or mineral oil is applied in order to scrape skin samples with the use of a scalpel.
Some doctors can also use a needle to extract a mite from the skin, and then examine the sample under the microscope to determine the type of mite. In some cases, an ink burrow test is also done. An ink burrow test involves putting washable ink on the itchy area, and after wiping it off, the burrows will absorb the ink to form a line.
Can Scabies be Cured?
Yes, scabies can be cured when treated. Itching lasts several weeks after treatment. Treatment involves the person with scabies and all other people that were in close contact with the patient, regardless of if they have any symptoms.
Treatment by a Doctor
It is important to treat this skin condition with proper medications. Generally, the condition is treated by prescription medications such as:
- 5% permethrin cream (most common)
- 10% Crotamiton cream
- 25% benzyl benzoate lotion
- Sulfur Ointment (5% to 10%) - Scabisil (available from Amazon)
- 1% Lindane lotion (not frequently prescribed due to side effects)
If stronger treatments are needed a Doctor may suggest Ivermectin.
The most common treatment for scabies is the medication Permethrin cream 5%. It is considered to kill mites faster and more effectively than Crotamiton (Eurax). Crotamiton 10% is not often used or prescribed because it is not as reliable in killing mites and their eggs.
Creams and lotions are be applied all over the body to avoid missing any locations where there may be mites. Creams are left on overnight (12 hours) and then thoroughly washed the following day. If you wash your hands during the 12 hours, reapply the cream to the hands.
Treatment may take approximately 1 to 3 days, with two treatments needed, one week apart. The purpose of the second treatment is to kill any mites that hatched after the first treatment.
Lice cream formulations are different than scabies creams. If you are pregnant or breast feeding always check with your Doctor before using any medication.
It is also important to treat every family member in order to completely eliminate the infestation.
Permethrin, Crotamiton and sulfur ointment 5-10% (Scabisil) are the only prescription medications that are used to treat pregnant and breastfeeding women and children below 2 years. Natural remedies for scabies are also available.
Doctors may also prescribe Lindane 1% if the problem still persists after using other medications. However, Lindane may possess some serious side effects that it should not be used for more than one application. It should not be used by pregnant and breastfeeding women, babies, individuals who are immunocompromised, and those who weigh less than 110 pounds.
Oral medication such as Ivermectin may be prescribed if patients do not respond to lotions and creams. Antihistamines (Benadryl) may be used to relieve itching. However, it is not meant to kill scabies.
If after treatment the skin still itches, then either the first treatment did not work due to resistance to the insecticide used or the burrows and secretions left behind by the scabies mite did not heal yet. In this case, additional treatments may be needed.
Itching can last for several weeks after treatment.
When applying a treatment it is important to treat the entire body, except the face. Ask your Doctor about any required exceptions to manufacturer directions. For example, the packaging may say stop at the neck, when the scalp should be treated as well. Also, instructions say to apply 2 treatments, when 3 are needed on days 1, 2 and 7. Do not put creams or ointments on the lips, nose, eye areas or mouth without consulting a dermatologist first.
the process has failed it is better to repeat it, as I have directed
using one of the older, and to be fair less pleasant preparations,
benzyl benzoate, which is still available.
In the meantime try a sedative antihistamine such as chlorpheniramine, (Piriton,) to help the itch.
How Often Do You Need to Wash Bedding?
For scabies treatment and prevention bedding only needs to be washed one time in a washing machine to kill any mites. Use a dryer to dry bedding. Wash bedding the same day you start treatment. As an alternative use a dry cleaner and keep items in the plastic wrapping.
Also, vacuum your home.
Do you need to treat pets?
Pets do not need to be treated for human mites.
Do you need to take a bath before treatment?
It is a good idea to take a shower or bath before treatment. Dry skin before applying any creams.
Home Treatment and Remedies
Mites can be treated with over the counter creams such as Scabisil. An alternative is to use a combination of Naturasil medicated Sulfur-Lavender soap combined with Dr. Berry's Sulfur Cream.
If you do not see results, visit a Dermatologist.
To help eliminate the problem, it is important to wash linens, bedding, and clothing in hot water that as worn up to 2 to 3 days prior to the scabies diagnosis. Also vacuum carpets and rugs, as soon as prescription or natural treatment starts in order to kill all live mites and their eggs.
To minimize the itching, soak a washcloth with clean and cool water and apply to irritated skin. Soothing lotions such as calamine lotion may be applied If itch persists, consider a remedy formulated to stop scabies itch such as Vanicream Itch Relief.
Scabies guide. Everything you need to know about how to identify and treat scabies. by: Michigan Department of Community Health
Scabies rash causes, biology, diagnosis, differential diagnosis, treatment, and prevention. by: Michigan Department of Community Health
(1)Journal of the American Board of Family Medicine
McCroskey, A. & Rosh, A. (2009), Scabies Retrieved on March 7, 2010
American Academy of Dermatology
Habif, Campbell, Chapman, et al. In: Dermatology DDxDeck. 2006. China. Mosby Elsevier. Card #92: Scabies.
Jacobson CC, Abel EA. Parasitic infestations. J Am Acad Dermatol 2007; 56: 1026-43
Chosidow O. “Clinical practices. Scabies.” N Engl J Med 2006; 354: 1718-27.
Habif, Campbell, Chapman, et al. In: Dermatology DDxDeck. 2006. China. Mosby Elsevier. Card #92: “Scabies.”
Jacobson CC, Abel EA. “Parasitic infestations.” J Am Acad Dermatol 2007; 56: 1026-43.
Steen CJ, Carbonaro PA, Schwartz RA. “Arthropods in dermatology.” J Am Acad Dermatol 2004; 50: 819 42, quiz 42-4.
Stone SP, Goldfarb JN, et al. “Scabies, other mites, and pediculosis.” In: Wolff K, Goldsmith LA, et al. Fitzpatrick’s Dermatology in General Medicine (seventh edition). McGraw Hill Medical, New York, 2008:2019-2032.