Crabs or Pubic Lice: How You Get Them and What to Do

    Published 24 December 2019
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    Reviewed by Marina Savchenko, MD, Pediatric Neurologist, Medical Consultant at Flo
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    Talking about crabs or pubic lice can be an uncomfortable topic. No one wants to get crabs, but it can happen to anyone. Learning what lice look like, where they come from, and how you get them can help you deal with this issue more easily. 

    What are pubic lice?

    Pubic lice, also known as crabs or genital crabs, are very small insects called Phthirus pubis that can infest your genital area. They’re different from head lice, and they got their nickname because they resemble crabs. Pubic lice are about 1/16 inch (1.6 millimeters) or less in size, making them very difficult to see.

    Pubic lice go through three developmental stages: eggs (nits), nymphs, and adult lice. Each of these stages has certain characteristics:

    • Nits — Lice eggs are very small and hard to see. They attach strongly to the hair shaft, have an oval shape, and are yellow or white. They take anywhere between 6 and 10 days to hatch.
    • Nymphs — These are still immature lice, and they look like smaller adult lice. Nymphs feed on blood and take approximately two to three weeks to mature into adults.
    • Adults — Adult lice look like tiny crabs with six legs, and they’re grayish-white or tan. Female lice are larger than males, and they need to feed on blood. Otherwise, they die within one or two days.

    How do you get lice?

    So, where do lice come from? In most cases, pubic lice are spread through sexual contact, which is why they’re usually found in adults. If found in children, pubic lice can be a sign of sexual abuse or sexual exposure. Pubic lice are often found in pubic hair, but they can also infest hair on other parts of the body, such as:

    • Legs
    • Armpits
    • Beards
    • Eyelashes
    • Eyebrows
    • Mustaches

    Lice can also be spread through personal items, such as clothing, bed linens, or towels, but this is less common. Some people believe that you can get pubic lice from sitting down on a toilet seat that has been used by an infested person, but this would be extremely unlikely. Lice can’t survive far from a human body, and they can’t hold onto smooth surfaces. Animals don’t get pubic lice.

    Anyone who finds that they have pubic lice should get tested for other sexually transmitted infections (STIs).

    Treatment of crabs

    You can use a 1-percent permethrin lotion or a mousse that contains compounds such as pyrethrins and piperonyl butoxide to get rid of crabs or pubic lice. These products are sold over the counter at most drug stores or pharmacies, so you won’t need a medical prescription to buy them.

    These products are safe and effective. However, there are certain steps you need to follow while using them:

    • Make sure you read the instructions written on the package and check the expiration date.
    • Wash your genitals and any other infested areas and towel dry.
    • Thoroughly apply the product on your pubic hair and any other areas that have been affected (except for eyelashes or eyebrows). Leave it on for the amount of time written on the instructions.
    • Remove the product following the instructions.
    • Most of the nits will still be attached to your hair, even after treatment. You can use your fingernails or a fine-toothed comb to remove nits.
    • Put on clean underwear once you finish the treatment.
    • Machine-wash and machine-dry your clothing, bedding, or towels at least two to three days before treatment. Use hot temperature settings for both machines.
    • Anything that can’t be machine-washed should be dry-cleaned or stored in a sealed plastic bag for at least two weeks.
    • Contact any sexual partners you’ve had in the previous month and let them know that they’re at risk for pubic lice and should get treatment.
    • Avoid sexual contact until both you and your partner have been treated and have ruled out a persistent infestation.
    • Use a lice-killing treatment in 9 to 10 days if you find live lice again.

    There are different prescription treatments available for persistent pubic lice infestations. However, these products aren’t routinely used as a first therapeutic option, and they require medical supervision. These treatments include:

    • Lindane shampoo — This medicated shampoo can kill lice and eggs, but it can also have toxic effects on the brain and nervous system. It should only be used by patients who can’t use other treatments or when other products have failed. The following people should not use lindane shampoo: pregnant or breastfeeding women, people with seizure disorders, people with irritated skin or open sores where the product should be applied, children, infants, seniors, and individuals who weigh less than 110 pounds (about 50 kilograms).
    • Malathion lotion 0.5% — Also known as Ovide, this product can kill lice but hasn’t been approved by the US Food and Drug Administration to treat pubic lice.
    • Ivermectin — Topical and oral ivermectin can kill lice; however, only topical ivermectin has been approved in the United States for this purpose.

    When to see a doctor about crabs

    Most cases of pubic lice can be resolved with over-the-counter treatments. However, you should consider seeking medical treatment if:

    • You’re pregnant or breastfeeding
    • You have skin wounds or abrasions from scratching that have become infected
    • Over-the-counter treatments haven’t been effective.

    Tips to prevent pubic lice

    Treating pubic lice is possible; however, if you can, it’s better to prevent them from occurring in the first place. Here are a few tips that might be useful:

    • Avoid having sexual contact or sharing bedding or clothing with anyone who has pubic lice.
    • Refrain from engaging in sexual activity until you have successfully completed treatment for crabs.
    • Contact any sexual partners that you’ve had within the last month and remind them that they should also get treated.

    A final note about crabs

    Pubic lice or crabs are tiny insects that can affect your genitals and other parts of your body. Pubic lice aren’t the same as head lice, and they’re usually acquired through sexual contact with an infested person. It’s also possible to catch lice if you share bed linens, clothing, or towels with someone who has crabs.

    Most cases of crabs can be successfully treated with over-the-counter products such as medicated shampoos and lotions. Resistant infestations could require prescription treatments and a trip to the doctor. Any sexual partners you’ve had recently will also require treatment. With good hygiene and proper treatment, you should be able to quickly get rid of pubic lice.

    History of updates

    Current version (24 December 2019)

    Reviewed by Marina Savchenko, MD, Pediatric Neurologist, Medical Consultant at Flo

    Published (24 December 2019)

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