Pubic lice (crabs) are tiny tan-to-grayish insects about the size of a pinhead, with a wide, crab-shaped body and claw-like front legs that grip coarse hair. Their eggs, called nits, are oval, yellowish-white specks cemented to the base of pubic hairs. Both are visible to the naked eye, especially with a magnifying lens.
with the right treatment
testing, not symptoms, decides
| Item | Value |
|---|---|
| Curable? | yes — with the right treatment |
| Tested by | exam + lab |
| Often | no symptoms |
| If you may have it | get tested — testing, not symptoms, decides |
What pubic lice actually are
Pubic lice are Pthirus pubis, blood-feeding insects that live mainly in coarse pubic and perianal hair, and sometimes spread to the armpits, chest, beard, or eyelashes CDC, About Pubic Lice. They're nicknamed "crabs" because under any magnification the adult looks like a squat crab: a broad body wider than it is long, with thick gripping claws on the second and third pairs of legs shaped to hold onto widely spaced, coarse hairs. That body shape is why they prefer pubic hair over the fine hair on your scalp. Head lice are a different, more elongated species.
You'll see three forms if you look closely. The adult is the largest, tan to grayish, and turns darker, almost rust-colored, right after a blood meal. The nymph is a smaller version of the adult that hasn't matured yet. The nits are the eggs, tiny oval capsules, yellowish to white, firmly glued to the side of a hair shaft near the skin, usually angled in one direction. Because they're cemented on, nits don't brush or flake off the way dandruff does.
What pubic lice look like vs. dandruff, scabs, and other look-alikes
The most useful test is whether the speck moves or detaches. Dandruff and dried skin flakes sit loosely on the hair and slide off with a fingernail; nits are glued in place and stay put. A scab from scratching is irregular and reddish-brown and lies on the skin, not bonded to a single hair. A live louse grips a hair near the skin and may move slowly when disturbed.
| What you see | Appearance | Tell-tale clue |
|---|---|---|
| Adult pubic louse | Pinhead-sized, tan/gray, crab-shaped, claw legs | Grips hair near skin; may move; darker after feeding |
| Nit (egg) | Oval, yellowish-white, smaller than a louse | Cemented to base of a hair; won't slide off |
| Dandruff / dry skin | White-gray flakes, irregular | Loose, brushes away easily |
| Scab | Reddish-brown crust | On the skin, not attached to one hair |
Symptoms — and the silent reality
Most infestations cause no symptoms at all CDC DPDx. You can carry pubic lice and feel nothing for a while, which is one reason they pass between partners unnoticed. When symptoms do appear, the classic one is itching in the genital area, often worse at night when the lice are more active. The itch is an allergic reaction to louse saliva injected during feeding, so it can take a couple of weeks after a new infestation to build up.
Beyond itching, you may simply see the lice or nits clinging to pubic hair. Persistent scratching can break the skin and lead to sores or a secondary infection, where bacteria get into the scratched skin and cause redness, tenderness, or oozing. Some people also notice tiny bluish-gray spots on the skin where lice have fed, or small dark flecks (louse droppings) in their underwear.
How pubic lice spread
Pubic lice spread mostly through sexual contact, because that's when coarse pubic hair meets coarse pubic hair long enough for a louse to crawl across. They can't fly or jump. Occasionally they pass through shared clothing or bedding, and a toilet-seat transmission is possible but very rare, since lice don't survive long off a human host and don't grip smooth surfaces well. Animals neither get nor spread pubic lice, so a pet is never the source. For the full picture, see how you get crabs.
How pubic lice are diagnosed
Diagnosis is visual: a clinician (or you) finds an actual crab louse or its nits on hair in the pubic region. They're visible to the naked eye, and a magnifying lens makes the call easier. There's no blood test or culture for crabs. You diagnose it by finding the insect or egg.
Because pubic lice are sexually transmitted, a diagnosis is a good prompt to screen for other infections that share the same exposure but show no signs of themselves. Many of those are diagnosed from a simple urine cup, a self-collected swab, or a quick exam, with results usually back in a few days, and they're free or low-cost at health departments, Planned Parenthood, and Title X clinics. If you've had a recent exposure, read when to test after exposure before you book, then get tested. You can also compare testing providers if you'd rather test at home.
Treatment
First-line treatment is an over-the-counter lice product applied to the pubic hair and affected areas: either a 1% permethrin lotion or a pyrethrins-with-piperonyl-butoxide mousse CDC, Treatment. If live lice are still present after the first application, you repeat treatment in about a week and a half. Wash and dry on hot heat any clothing, towels, and bedding used in the days before treatment to kill any lice or eggs that fell off.
Eyelash infestations are a special case where you do not put insecticide near the eyes. Instead, an ophthalmic-grade petrolatum (not ordinary Vaseline) is applied to the lash margins as directed CDC STI Guidelines. Whatever you use, finish the full course even once the itching eases, and ask whether your partner needs treating so you don't pass it back and forth. For a step-by-step walkthrough, see how to get rid of crabs at home.
Complications if left untreated
Pubic lice themselves don't carry the dangerous diseases some other parasites do, but ignoring them isn't harmless. Constant scratching can cause excoriation, raw broken skin from repeated scratching, that opens the door to a secondary bacterial skin infection, which may need antibiotics. The infestation also keeps growing and stays contagious to every partner until treated. And because crabs travel with the kind of close contact that transmits other STIs, an untreated case often means co-infections are going unchecked too.
Prevention and avoiding reinfestation
The most reliable prevention is avoiding skin-to-skin and sexual contact with someone who has an active infestation until they're treated. Condoms used every time lower the risk of the STIs that travel alongside crabs, though they don't fully cover the hair-bearing skin where lice live. After a diagnosis, tell all sex partners from the past month so they can be checked and treated, hold off on sexual contact until both of you are clear, and decontaminate bedding and clothing, or you can re-infest each other in a loop. Practical details are in how to prevent crabs & avoid reinfestation.
When to see a clinician
See a clinician if over-the-counter treatment doesn't clear live lice after the repeat application, if the skin becomes red, warm, swollen, or oozing (signs of a secondary infection), if lice involve the eyelashes, or if you're pregnant or breastfeeding and unsure which product is safe. Clinics handle this routinely.