Pubic Lice – Causes, Signs and symptoms

Pubic Lice

Also called: Crabs, Genital Lice, Pediculus Pubis, Pubic Louse, Genital Crabs, Pediculus Pubis Infestation, Genital Louse, Pubic Crabs

Reviewed By:
Vikram Tarugu, M.D., AGA, ACG


Pubic lice (sometimes called crabs) are parasites that infest the pubic region and other areas of the human body that have coarse hair. These parasites are usually transmitted through sexual contact. Less commonly, they may be spread through nonsexual physical contact (e.g., sharing towels, clothing or a bed with an infested person).

Pubic lice or their eggs (called nits) may be found on shafts of coarse hair, or on the skin of the pubic region. Occasionally, pubic lice may be found on eyelashes, eyebrows, legs or in facial hair. The primary symptom of infestation is itchiness. Scratching often causes the affected area to become red, raw and irritated. Sometimes, skin lesions may develop.

Pubic lice are diagnosed by a visual examination of the affected area. This can be done by a physician or by the patient or friend or loved one of the patient. If inspection of the area is done at home, a magnifying glass may be necessary.

There are a variety of over-the-counter and prescription medications used to treat a pubic lice infestation. Most commonly, a special cream or shampoo is used. These medications kill the lice, but not the nits. Nits can be removed from the area using a fingernail or specially designed comb. Treatment may need to be repeated to eliminate all lice and nits from the area.

Sexual activity should not be resumed until treatment is completed. Any personal item handled by an infested person should be washed in hot water and dried for at least 20 minutes to kill any pubic lice that may remain on these items. Anyone diagnosed with or treated for pubic lice should inform all sexual partners that they have exposed to pubic lice. This helps prevent the spread of infestation.

The best way to prevent an infestation of pubic lice is to avoid sexual or other close contact with infested persons, including contact with their clothing, bedding or towels. Condoms or other methods of safe sex do not protect against the spread of pubic lice. People with pubic lice may have contracted other sexually transmitted diseases and should talk with their physician about that possibility and the best course for diagnosis, treatment or prevention.

About pubic lice

Pubic lice are wingless parasites (Pthirus pubis) that must have a human host to survive. They prefer to cling to the coarse hairs of the pubic region or any other location on body with this type of hair (e.g., eyebrows, eyelashes, armpits, legs, facial hair). They feed on human blood, and the human body is their sole host. Pubic lice are not carried or spread by animals.

Pubic lice are transmitted primarily through sexual contact. For this reason, a pubic lice infestation is considered a type of sexually transmitted disease or, more recently, a sexually transmitted infection (since carrying pubic lice is not technically a disease). Less often, they are passed from human to human via clothing, bedding and towels that are contaminated. While pubic lice do not carry disease (unlike body lice), people who have a pubic lice infestation may be at risk of contracting other sexually transmitted diseases.

Pubic lice are also known as “crabs” because they resemble crabs when viewed under a microscope. The bodies of pubic lice are shorter and rounder than those of head lice. Pubic lice are tan to grayish-white in color. Pubic lice are not able to fly. Their crablike claws allow them to cling to course hairs of the human body, but do not allow them to move easily about on smooth surfaces.

Adult females are slightly larger than adult males. After mating, the female lays eggs (called nits). One female can lay up to three nits per day over the course of about 10 days. These white or yellow oval-shaped nits are smaller than a grain of rice and can be difficult to see. Each nit is firmly attached to a coarse shaft of hair. Pubic lice hatch from nits about one week after being laid.

Newly hatched pubic lice (called nymphs) secure themselves to the base of a coarse shaft of hair and begin to feed on its human host. As pubic lice suck blood from their host, saliva and other irritating components are released, causing itchiness. Pubic lice also deposit black feces in the area. Nymphs mature into adult pubic lice in about seven days.

Pubic lice must consume human blood to survive. These lice can only live for 24 to 48 hours without a fresh intake of blood, such as when the lice become dislodged from their host.

A pubic lice infestation is extremely rare in infants and children. When infestation occurs, the lice may be found clinging to a child’s eyelashes or eyebrows. Pubic lice may cause inflammation of the eyelid (blepharitis) in children and adults, although pubic lice are not the only cause of this condition. Pubic lice in young children or prepubescent teens are usually spread from a parent who is infested (e.g., sharing contaminated bedding, clothes or towels), although they may indicate sexual activity or sexual abuse.

Skin redness and irritation due to scratching are common complications in people with pubic lice. In some cases, skin lesions may develop in the area. 

Pubic lice are one of three different kinds of lice that are human parasites. The other two are:

  • Head lice. These lice infest hair on a person’s head. Head lice are common in children and outbreaks are common at school, daycare centers and other group settings where children have close contact with one another. Unlike pubic lice, head lice are not sexually transmitted.

  • Body lice. Sometimes called bed lice, these lice are most common among unwashed, transient groups of people (e.g., homeless people). They live in the seams of unwashed clothing and bedding, and are the only human lice that can carry and spread disease (e.g., typhus). Body lice are also not sexually transmitted.

It is unclear exactly how many cases of pubic lice infestation are diagnosed every year. It may be difficult to track because of the stigma attached to sexually transmitted diseases. In addition, many people diagnose the problem themselves and are able to treat the condition with over-the-counter medications in the privacy of their own homes.

Risk factors and causes of pubic lice

In most cases, a pubic lice infestation is caused by exposure to another person with pubic lice, usually through sexual activity or other close bodily contact (e.g., sleeping in the same bed). In some cases, it may occur as the result of contact with personal objects (e.g., clothes, bedding, towels) recently used by a person with pubic lice.

Contrary to popular belief, it is not likely that pubic lice are spread via toilet seats, according to the Centers for Disease Control and Prevention. Their clawlike feet do not allow them to walk or grasp onto smooth surfaces such as a toilet seat. In addition, pubic lice are not able to survive very long when away from a human host.

People who may be at an increased risk of contracting a pubic lice infestation include:

  • Sexually active people under 40
  • Men and women with multiple sex partners
  • Men and women whose partners have multiple sex partners
  • People in crowded living conditions

Pubic lice infestations are extremely rare in infants and children, as well as in prepubescent children.

Signs and symptoms of pubic lice

There are several signs and symptoms of a pubic lice infestation, although some people may be asymptomatic. The primary sign is itchiness (pruritus) of the pubic area. Itchiness in other areas of the body with coarse hair (e.g., eyebrows, eyelashes, armpits, legs, facial hair) is less common. Skin in the area may become red, raw and irritated due to scratching.

If the skin is broken due to scratching, secondary infections of the skin (e.g., impetigo) may occur (e.g., if bacteria from the fingernails are introduced to the area).  Tiny pale blue skin lesions (maculae ceruleae) may appear on their inner thighs and/or lower abdomen. Although a distinctive sign of a pubic lice infestation, maculae ceruleae syndrome is not common. It is found most often in people with severe pubic lice infestations.

Another sign of a pubic lice infestation is the presence of white or yellow nits (eggs) clinging to shafts of coarse hair in the pubic region or other areas of the body. Nits are firmly attached to the hair and will not be as easily removed as dandruff or crumbs might be. Pubic lice may be difficult to see because their tan to grayish-white color may blend in with a person’s skin color – although they may be seen with a magnifying glass. Pubic lice also tend to move quickly away from light.  

Sometimes, feces from pubic lice may be seen on underwear or bed linens. These may appear as tiny black specks or flakes that do not move.

Diagnosis methods for pubic lice

Diagnosis of a pubic lice infestation involves a visual examination of the hair and skin in the pubic region to look for eggs (nits) attached to hair shafts or crawling pubic lice. Physical examination may also reveal areas of irritation or skin lesions. Other areas of the body may be examined as well, including the armpits, legs, eyebrows and eyelashes, and facial hair.

A physician may make the diagnosis, or people can examine themselves or another person at home (in which case, a magnifying glass may be needed).

People who have a pubic lice infestation may also have contracted other sexually transmitted diseases. Additional tests may be necessary to diagnose other STDs.

Treatment options for pubic lice

For most pubic lice infestations, treatment involves using special lotions or shampoos that kill the lice (a pediculicide).

Lice-killing shampoos and lotions that contain 1 percent of the active ingredient permethrin or pyrethrin are available over the counter. They are usually applied to all affected areas (excluding the eyes), left on for a few minutes to a few hours and then rinsed off. All lotions or shampoos should be applied and rinsed off according to the manufacturer’s directions, because treatment times will vary depending on the product. Prescription strength lice-killing lotion may also be available.

Lotions or shampoos containing the ingredient lindane are no longer recommended because of the risk of serious side effects such as seizures and, in rare cases, death. Patients should consult their physician about their risks before using any product with lindane.

Special lotions or shampoos do not kill pubic lice eggs (nits), which may still be attached to hair shafts. Nits can be removed with the fingernails, tweezers or by using a specially designed fine-toothed comb called a nit comb. Using such a comb rids the area of dead pubic lice as well. Occasionally, some pubic lice may survive treatment and need to be combed out. Any live lice can be placed in a drop of the medicated lotion or shampoo to kill it.

Removing pubic lice and nits using only a nit comb (without prior use of a medicated lotion or shampoo) may also work as a treatment, although it is considerably more time-consuming. This may be helpful when just a few pubic lice or nits are found, or when they are found in the eyebrow or eyelash area. Shaving all hair from the affected area may rid the area of pubic lice, but is often not necessary. Shaving should not be done in certain areas (e.g., around the eyes).

A single treatment may not rid the area of all pubic lice. Multiple treatments may be required, often administered a week apart. This can help ensure any nits that survived the initial treatment have not hatched lice since treatment was applied. In addition, certain types of medications may sometimes fail to treat a pubic lice infestation due to increasing incidents of drug resistance.

Certain oral medications may also be available by prescription. This may be particularly helpful for people with pubic lice on the eyelashes or in cases where pubic lice are near the rectum. However, these systemic medications are not recommended for pregnant or breastfeeding women or children weighing 33 pounds (15 kilograms) or less. For infestation of the eyelids, a special petroleum ointment may be available by prescription. Over-the-counter petroleum gels should not be used.

Clean underwear and clothing should be put on after treatment. Personal items should be cleaned if they have been recently handled (within a day or two of treatment) by a person infested with pubic lice. In order to kill lice and nits in bedding, clothing and towels, these items should be washed in hot water – at least 130 degrees Fahrenheit (54 degrees Celsius) – and dried on the hot dryer cycle for at least 20 minutes. Items that are not washable should be dry cleaned, or may be kept sealed in an airtight bag for two weeks. Carpeted areas should be vacuumed.

Sexual activity should be avoided until treatment of all infected persons is completed. Also, it is important to treat all sexual partners of an infested person at the same time, to prevent reinfestation.

Prevention methods for pubic lice

The best way to prevent an infestation of pubic lice is to avoid sexual or other close contact with infested people. Use of a condom or other forms of safe sex will not prevent the spread of pubic lice. It is important to be aware of any potential health concerns of all sexual partners. Maintaining a monogamous relationship can help reduce the likelihood of being exposed to pubic lice.

Pubic lice may sometimes be spread through physical contact with contaminated linens or clothing. Avoid sharing towels at the gym and sharing or trying on swimsuits. It is also important to wash bedding, clothing and towels regularly in hot water – at least 130 degrees Fahrenheit (54 degrees Celsius) – and dry on high heat for at least 20 minutes.

People diagnosed or treated for a pubic lice infestation should inform all sexual partners that they have been exposed to pubic lice. This can help prevent the spread of infestation.

Questions for your doctor regarding pubic lice

Preparing questions in advance can help patients have more meaningful discussions with healthcare professionals regarding their conditions. Patients may wish to ask their doctor the following questions related to pubic lice:

  1. How can I tell if I have a pubic lice infestation?
  2. Where else on my body may the pubic lice go?
  3. How might I have been exposed to pubic lice?
  4. If I was exposed to pubic lice through sexual contact, what other sexually transmitted diseases could I be at risk for?
  5. What treatment do you recommend for pubic lice? How long will I need to use it?
  6. Will shaving help get rid of them? Do I need medication in addition to shaving?
  7. How can I be sure all the lice and eggs (nits) are gone?
  8. Does the rest of my family or other household members need to be treated, too?
  9. When is it safe to resume sexual activity without the risk of pubic lice infesting my partner?
  10. How do I get pubic lice out of my bedding, clothing and towels?
  11. How are pubic lice different from head lice or body lice?
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