• Also Known As:
  • Crabs Testing
  • Crab Lice Testing
  • Crab Louse Testing
  • Phthiriasis Testing
  • Pediculosis Pubis Testing
  • Nit Testing
  • Formal Name:
  • Pubic Lice Test
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Test Quick Guide

Pubic lice are small, parasitic insects that feed on blood and can infest a person’s pubic or genital area. Having lice is called pediculosis. Pediculosis with pubic lice is a sexually transmitted disease (STD) that can be easily spread through close contact with an infected person. While that usually means sexual contact, it is also possible to get pubic lice if you share a person’s clothing, towels, or other personal items.

Pubic lice testing involves looking for signs of lice on the body. Testing is typically ordered when a person has symptoms of a pubic lice infestation.

About the Test

Purpose of the test

The purpose of pubic lice testing is to diagnose pediculosis caused by an infestation of pubic lice. Pubic lice testing involves various methods of looking for these insects on the body.

While lice can sometimes be seen with the naked eye, a health professional may conduct a closer examination to make a diagnosis. Additional ways of finding pubic lice include:

  • A magnifying glass may be needed to see individual pubic lice or eggs, which are called nits.
  • Wood’s lamp examination involves a special UV light that is held near the patient’s skin. Lice and other skin conditions have a characteristic appearance under a Wood’s lamp.
  • Dermoscopy describes a procedure in which a doctor uses an instrument called a dermatoscope to look closely at the skin. This procedure can help distinguish live nits and lice from empty eggs or other skin conditions.

In some cases, a doctor may use a piece of cellulose tape, also called packing tape, to collect lice for examination. Tape can be applied to the area of a suspected infection, then removed and placed on a glass slide that can be looked at under a microscope for evidence of lice.

What does the test measure?

There are three types of lice that live on the human body: pubic lice, head lice, and body lice. Pubic lice testing looks for evidence of Pthirus pubis, which is the scientific name for the pubic or crab louse. Pubic lice live on the human body and go through several life stages:

Nits are the name of lice eggs. Female pubic lice lay around 30 nits during their lifespan. Nits are oval-shaped, white or yellow in color, and found firmly attached to body hair. These eggs are so small that they are difficult to see with the naked eye. Nits remain attached to the hair for 6 to 10 days before hatching and become nymphs.

Nymphs are young lice that mature for several weeks and become adult lice. In order to survive, nymphs must begin to feed on human blood. While nymphs may be visible without the use of special tools, they are smaller and more difficult to spot than adult pubic lice.

Adult pubic lice live and reproduce only on the human body. When viewed under a magnifying glass, these insects are grey to white in color and have six legs. Pubic lice cannot jump or fly. They move around the body by crawling between hair shafts. If an adult is removed or falls off of its human host, it cannot survive for more than one or two days.

When should I get a pubic lice test?

Pubic lice testing is most often ordered when a person has symptoms of an infestation. Symptoms of pediculosis are caused by bites from adult lice and nymphs. Symptoms may include:

  • Itching in the pubic area
  • Red or bluish spots on the skin of the abdomen, thighs, or buttocks
  • Sores or skin infections due to scratching
  • Small blood stains or dark brown specks on underwear
  • Swollen lymph nodes in the groin

After getting pubic lice, it may take up to two to four weeks for symptoms to begin. Itching is the most common symptom and is caused by the body’s allergic reaction to bites.

Although less common, pubic lice can live on coarse hair in other places on the body such as the armpits, eyelashes, and eyebrows. Infections in these areas can cause itching, burning, or redness and irritation.

Testing may also be recommended after a person comes into contact with someone diagnosed with pubic lice. In addition to sex and physical contact, transmission can occur through sharing objects such as:

  • Bedding, including sheets and blankets
  • Bathing suits
  • Towels

Finding a Pubic Lice Test

How to get tested

Testing for pubic lice can be conducted at home or in a medical setting like a doctor’s office.

While pubic lice can sometimes be seen with the naked eye or a magnifying glass, doctors may recommend additional testing to look closer at the area of suspected infestation.

Can I take the test at home?

Pubic lice can often be found at home by inspecting pubic hair for evidence of lice or nits. If lice are found or suspected, additional follow-up with a doctor is helpful to confirm the presence of lice and get recommendations for appropriate treatment.

How much does the test cost?

The cost of pubic lice testing depends on who performs the test and where it is conducted. When pubic lice testing is performed by a doctor or health care provider, the cost of testing may be covered by a person’s health insurance. Out-of-pocket costs may include copays and deductibles.

Testing for pubic lice may also be available at community-based organizations and through local health departments for free or at a reduced cost.

Taking a Pubic Lice Test

Pubic lice testing is performed by looking for evidence of lice or nits near a person’s pubic area. Although less common, evidence of pubic lice may be found on other parts of the body. Testing to confirm a diagnosis of pubic lice and rule out other skin problems is done by a health care provider in a medical setting like a doctor’s office or health clinic.

Before the test

There are no special preparations needed before a pubic lice test, although it’s important for patients to tell their doctor about any symptoms they’ve experienced and whether they have been treated for a pubic lice infestation in the past.

During the test

During a pubic lice test, a patient will be asked to remove clothing from the part of the body where lice are suspected. The health care provider will then visually examine hair for pubic lice or nits. In most cases, this examination focuses on the pubic area around the genitals.

When pubic lice are difficult to find, a tool such as a magnifying glass, Wood’s lamp, or dermatoscope may be used to look more closely at the hair shaft.

Depending on a patient’s symptoms and age, a doctor may also look for pubic lice on other areas of the body including:

  • Eyebrows
  • Eyelashes
  • Beard
  • Mustache
  • Armpit
  • Near the anus
  • Torso
  • Scalp

After the test

There are no risks or side effects of looking for pubic lice. Normal activities can be resumed after the test is finished.

Pubic Lice Test Results

Receiving test results

Results of pubic lice testing are typically available right after the test is completed. The health care provider who performed the test will likely discuss test results immediately and offer recommendations for treatment.

Interpreting test results

Pubic lice test results are reported as positive or negative. Test results indicate whether evidence of the parasitic insect Pthirus pubis was detected on the body.

A positive test result means that pubic lice or eggs were found during the evaluation.

A negative test result means that pubic lice were not detected on the body.

Are test results accurate?

Looking for pubic lice is an essential tool to find and treat this STD. In some cases, pubic lice can be difficult to find without a tool to magnify and look closely at a person’s pubic hair. Other skin disorders may cause similar symptoms as pubic lice, but a close examination can effectively differentiate these conditions.

Do I need follow-up tests?

If living lice or eggs are found during a pubic lice test, follow-up testing is important after the patient has completed treatment. This follow-up examination helps to ensure that all lice have been eliminated. After a positive pubic lice test, a person’s sexual partners should be tested and treated as well.

STD testing is also recommended for people diagnosed with pubic lice. Follow-up tests may include gonorrhea testing, chlamydia testing, syphilis tests, and HIV testing.

If a doctor suspects pubic lice but no lice or nits are found during an examination, the doctor may order a fungal culture to rule out a fungal infection as the cause of the patient’s symptoms.

Questions for your doctor about test results

It may be helpful to ask your doctor questions about pubic lice and the results of pubic lice testing. Questions may include:

  • Was any evidence of pubic lice found during the exam?
  • What else might be causing my symptoms?
  • Based on my results, are any follow-up tests necessary?
  • What should I share with my sex partners about my test result?

View Sources

A.D.A.M. Medical Encyclopedia. Pubic lice. Updated November 2, 2021. Accessed November 19, 2021. https://medlineplus.gov/ency/article/000841.htm

American Sexual Health Association. Crabs. Date unknown. Accessed November 19, 2021. https://www.ashasexualhealth.org/crabs/

Centers for Disease Control and Prevention. Pubic “crab” lice: Biology. Updated June 26, 2019. Accessed November 19, 2021. https://www.cdc.gov/parasites/lice/pubic/biology.html

Centers for Disease Control and Prevention. Pubic “crab” lice: Diagnosis. Updated September 12, 2019. Accessed November 19, 2021. https://www.cdc.gov/parasites/lice/pubic/diagnosis.html

Centers for Disease Control and Prevention. Pubic “crab” lice: Frequently asked questions (FAQs). Updated September 17, 2020. Accessed November 19, 2021. https://www.cdc.gov/parasites/lice/pubic/gen_info/faqs.html

Davidson MH. Lice (pediculosis). Merck Manuals Professional Edition. Updated May 2020. Accessed November 19, 2021. https://www.merckmanuals.com/professional/dermatologic-disorders/parasitic-skin-infections/lice

Dinulos JGH. Lice infestation. Merck Manual Consumer Edition. Updated June 2020. Accessed November 19, 2021. https://www.merckmanuals.com/home/skin-disorders/parasitic-skin-infections/lice-infestation

Goldstein BG, Goldstein AO. Pediculosis pubis and pediculosis ciliaris. In: Dellavalle RP, Levy ML, Rosen T, eds. UpToDate. Updated March 24, 2021. Accessed November 19, 2021. https://www.uptodate.com/contents/pediculosis-pubis-and-pediculosis-ciliaris

Goldstein BG, Goldstein AO. Office-based dermatologic diagnostic procedures. In: Dellavalle RP, ed. UpToDate. Updated April 14, 2021. Accessed November 19, 2021. https://www.uptodate.com/contents/office-based-dermatologic-diagnostic-procedures

Goldstein BG, Goldstein AO. Scabies: Epidemiology, clinical features, and diagnosis. In: Dellavalle RP, Levy ML, Rosen T, eds. UpToDate. Updated September 13, 2021. Accessed November 19, 2021. https://www.uptodate.com/contents/scabies-epidemiology-clinical-features-and-diagnosis

Goldstein BG, Goldstein AO. Patient education: Pubic lice (beyond the basics). In: Dellavalle RP, Levy ML, eds. UpToDate. Updated December 13, 2021. Accessed November 19, 2021. https://www.uptodate.com/contents/pubic-lice-beyond-the-basics

Guenther LCC, Maguiness S. Pediculosis and pthiriasis (lice infestation) workup. In: Bronze MS, ed. Medscape. Updated March 24, 2021. Accessed November 19, 2021. https://emedicine.medscape.com/article/225013-overview

Marghoob AA, Jaimes N. Overview of dermoscopy. In: Tsao H, ed. UpToDate. Updated September 9, 2019. Accessed November 19, 2021. https://www.uptodate.com/contents/overview-of-dermoscopy

MedlinePlus: National Library of Medicine. Pubic lice. Updated April 18, 2018. Accessed November 19, 2021. https://medlineplus.gov/pubiclice.html

UpToDate. Patient education: Lice (the basics). Date unknown. Accessed November 19, 2021. https://www.uptodate.com/contents/lice-the-basics

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