Crabs, or pubic lice, spread primarily through sexual contact. The lice crawl from one person’s body hair to another’s during close physical contact, and they cannot jump or fly. While non-sexual transmission is possible, it accounts for a small fraction of cases.
Sexual Contact Is the Main Route
Pubic lice live in coarse body hair, most commonly in the genital area. During sex or other intimate skin-to-skin contact, the lice simply walk from one person to another. This doesn’t require penetration. Any prolonged body-to-body contact where hair-bearing areas touch can be enough. Condoms do not reliably prevent transmission, because the lice live in surrounding hair that condoms don’t cover.
The lice are tiny (about 1 to 2 millimeters), flat, and crab-shaped, which is how they got their nickname. They’re distinct from head lice: shorter, wider, and specifically adapted to grip the thicker, more widely spaced hairs found on the pubic area, armpits, chest, and occasionally eyebrows or eyelashes.
Can You Get Crabs From Bedding or Toilet Seats?
Occasionally, pubic lice spread through shared clothing, towels, or bedding. This happens because a louse or its eggs can cling to fabric after falling off a host. However, adult lice need human blood to survive and die within 24 to 48 hours without a meal. That narrow survival window makes indirect transmission uncommon.
Toilet seats are an even less likely source. The CDC lists toilet seat transmission as very rare, and it would require sitting on a seat immediately after an infested person used it. Lice have no reason to leave a warm human body for a cold, smooth surface, and their claw-like legs are designed to grip hair, not porcelain. For practical purposes, you can stop worrying about public restrooms.
How Long Before You Notice
After your first exposure, it can take one to three weeks before itching starts. That delay happens because the itching is an allergic reaction to lice saliva, and your immune system needs time to develop that sensitivity. The itch tends to be worse at night. Some people also notice small bluish-gray spots on the skin where lice have been feeding, or tiny dark specks (louse droppings) in their underwear.
If you’ve had pubic lice before, the itching may start sooner because your body already recognizes the allergen. Either way, by the time you feel symptoms, the lice have likely been present for days or weeks and may have laid eggs (called nits) that are glued to hair shafts close to the skin.
Where They Live on the Body
Pubic hair is the most common site, but crabs can also infest other areas with coarse hair: armpits, leg hair, chest hair, beards, and in rare cases, eyebrows and eyelashes. They do not infest the scalp. Head hair is too fine and densely packed for their claws to grip effectively. That’s a key difference from head lice, which are adapted for the opposite environment.
In children, eyelash infestation is the most common presentation. When a child has pubic lice on their eyelashes, it may indicate close household contact with an infested adult, typically through shared bedding rather than sexual contact.
How Treatment Works
Over-the-counter insecticidal washes containing permethrin are the standard first-line treatment. You apply the product to all affected areas, leave it on for the recommended time (usually about 10 minutes), and rinse. A second application about 9 to 10 days later kills any lice that hatched from surviving eggs after the first treatment.
You’ll also need to machine-wash all clothing, towels, and bedding used in the two days before treatment in hot water, then dry on high heat. Items that can’t be washed should be sealed in a plastic bag for two weeks, which is long enough to starve any remaining lice. Sexual partners from the past month should be notified and treated at the same time, even if they don’t have symptoms yet, to avoid passing lice back and forth.
For eyelash infestations, standard insecticidal washes are too harsh. A thick layer of petroleum jelly applied to the lashes several times a day for a week or more can suffocate the lice without irritating the eyes.
Why Cases Have Declined
Pubic lice infestations have dropped significantly over the past two decades. The most widely cited explanation is the rise of pubic hair grooming and removal. With less hair available, the lice have fewer places to attach and lay eggs. This doesn’t mean crabs have disappeared. They still circulate, and anyone with pubic or coarse body hair who has close contact with an infested person remains at risk. Having multiple sexual partners increases your chances simply because it increases the number of potential exposures.