Pubic lice (“crabs”): recognition, symptoms, and treatment

General information about Pubic lice

To help you understand whether you have pubic lice, below are some important facts about these little parasites.

How you get pubic lice

Pubic lice are transmitted from one person through:^{1, 2, 3}

• Sex, the most common way (people get them from direct skin-to-skin contact during intercourse)
• Other skin-to-skin contact (hugging, kissing)
• Personal objects (towels, bedding, clothes)

Remember, condoms and other contraception methods do not prevent pubic lice transmission.

It is almost impossible to get pubic lice through toilet seats since this parasite is unable to survive without its host (a human being).

The symptoms of pubic lice

Symptoms usually develop five days after exposure. People suddenly start to experience itching in the genital and anal area, which often intensifies at night.²

Some people may also experience:

• Weakness
• Low-grade fever
• Irritability
• Conjunctivitis (people who have “crabs” in their eyelashes)

At-risk people

Pubic lice mainly affects adult, sexually active people.

However, children who share beddings and towels with infected family members are also at risk. Remember, sometimes, finding “crabs” on a child may be a sign of sexual abuse. The parasites usually appear on their head and in their eyelashes.^{1, 2}

Pubic lice are common and easily spread

Pubic lice are quite common. They affect about 2%–10% of the world’s population regardless of socioeconomic level, race, or ethnicity. Around 3 million pubic lice cases are reported in the United States every year.¹

It is difficult to estimate how likely a person is to get pubic lice from one-time sex. But “crabs” are known to spread easily from one person to another during sexual intercourse. Therefore, the chance of getting them is considered to be high.

What pubic lice look like

To determine whether you have been exposed to pubic lice, you need to know what these insects look like. And you should also know what it is like to experience pubic lice–related health complications.

These parasites have three forms:⁴

• Nit
• Nymph
• Adult

Detailed descriptions of all three forms are presented below.

Form	Photo	Main characteristics
Nit (egg)	Image source: https://www.wikiwand.com/en/Crab_louse	Shape Oval attached to the hair Size 0.8 mm in length Color Yellowish-white
The Nymph	Image source: https://www.rxlist.com/collection-of-images/crabs_pubic_lice_picture/pictures.htm	Shape crablike (that’s how they got their “nickname”) 6 legs (the 2 frontal legs are larger than others) Size about 1 mm in length Color Yellowish-white
The Adult	Image source: Daniel J. Drew - Gall L (2019). Invertebrate Zoology Division, Yale Peabody Museum. Yale University Peabody Museum.	Shape same as nymph Size 1.1-1.8 mm in length females larger than males Color tan; grayish-white; darker then nymphs because they are consuming more blood

Pubic lice can cause skin conditions

In addition to excessive itchiness, pubic lice may lead to mild skin conditions:5

• Tiny reddish bumps or spots on the affected area
• Bluish spots on the thighs
• Bluish spots on the lower abdomen

The pictures below illustrate these skin conditions:

Image source: https://medicine.uiowa.edu/dermatology/crab-lice

Comparison to other similar conditions

Now you know how to recognize pubic lice and related skin conditions. However, some other conditions have a similar appearance. To help you distinguish them, see the photos below.

Pubic lice treatment

If you suspect or know that you have pubic lice, seeing a doctor is recommended. He or she may test you for other STDs as well since they often co-exist with pubic lice. On the basis of your condition, the doctor will prescribe you one of the following treatment options.

There are widely available over-the-counter medications that will help to get rid of pubic lice:6

• Lotions that contain 1% permethrin
• Mousses that contain pyrethrins and piperonyl butoxide

Also, there are more-toxic products that can kill the nits. These are prescription medications and should not be considered as a first option. These medications include:

• Lindane shampoo (may have serious side effects, so should be used only by patients who were not able to successfully treat the condition with other medications)
• Malathion* lotion 0.5% (Ovide*). This medication is not approved by the US Food and Drug Administration (FDA)

Follow-up treatment may be needed

You will probably get rid of the adult lice with the help of medication. However, the nits may resist the medication and transform into adult lice after a few days, continuing the cycle.

To ensure maximum effectiveness of the treatment, it is recommended that the anti-lice medication be reapplied seven days after the initial application. Patients should also make sure that there are no lice a week after the second application.3

How pubic lice affect having sex

You should avoid sex until you and your sexual partner(s) is/are treated. You can have sex as soon as you are pubic lice–negative in a follow-up evaluation.