Recurring crabs almost always come from one of three fixable gaps: live nits that survived the first treatment and hatched, an untreated sex partner who reinfects you, or bedding and clothes that were never decontaminated. Drug failure is rare. When crabs come back, it usually means the louse life cycle was interrupted but not finished, so it simply restarted.
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 |
Why crabs keep coming back
Pubic lice are Pthirus pubis, tiny crab-shaped insects that feed on blood and grip coarse pubic and perianal hair (and sometimes the armpits, chest, beard, or eyelashes) CDC. They spread mostly through skin-to-skin sexual contact. Their life cycle explains recurrence: adult lice lay nits (eggs) cemented to the hair shaft, and those eggs hatch days later. A treatment that kills the adults but leaves viable eggs behind buys you only a brief, false sense of being cured.
The most common reasons an infestation returns:
- Surviving nits. Over-the-counter permethrin and pyrethrin products are far better at killing crawling lice than at killing eggs. If you skip the repeat application, eggs that survived the first round hatch into a new generation of lice. The CDC says to repeat treatment in 9–10 days if live lice remain CDC treatment.
- Partner re-exposure. If a sex partner wasn't treated at the same time you were, you can clear your own infestation and then catch it right back the next time you have contact, a ping-pong cycle that can repeat for weeks.
- Laundry and bedding gaps. Lice and nits can linger briefly on items that touched your body in the prior two to three days. Untreated sheets, towels, and underwear are a small but real source of reinfestation if they're not hot-washed.
- Incomplete coverage. Missing patches of coarse hair, like the perianal area, upper thighs, lower abdomen, or the beard, leaves a pocket of lice to repopulate.
It's usually not treatment failure
When people see crabs again, they often assume the medicine didn't work and reach for something stronger. Most of the time the medicine worked fine on the lice it touched. The problem was the eggs, the partner, or the laundry. Recurrence and resistance are not the same thing, and treating it as resistance leads people to over-apply insecticide to skin that's already irritated.
Two steps prevent the ping-pong effect more than any product swap. First, tell every sex partner from the past month so they can be treated, and avoid sexual contact until both of you have finished treatment CDC STI guidelines. Treating yourself while your partner stays infested is the single most common reason crabs "keep coming back." Second, decontaminate bedding and clothing at the same time, not days later.
Because pubic lice can travel with other sexually transmitted infections, a return visit is also a reasonable moment to think about broader screening. There's a sensible window to wait for accurate results — see when to test after exposure — and you can get tested for the infections that show no symptoms at all.
How to tell reinfection from a missed cure
This distinction changes what you do next, so slow down and look closely. A missed cure (the first treatment never fully worked) and a reinfection (you cleared it, then caught it again) can feel identical, but the clues differ.
- Look for live, moving lice versus empty nit shells. Crawling lice mean an active infestation. Nits alone, especially pale, empty shells far out along the hair shaft, can persist after a cure and don't always mean ongoing infestation. A magnifying lens helps you tell the difference; here's what pubic lice look like up close.
- Timing matters. Itching that never improved after treatment points to a missed cure. Itching that cleared for a week or two and then returned points to reinfection, often from an untreated partner or contaminated bedding.
- Itch can lag. Itching is an allergic reaction to louse bites and can linger for a short time after the lice are dead, so post-treatment itch by itself isn't proof of failure. Check for live lice before re-treating.
If you're unsure what you're seeing, review the crabs symptoms and inspect under good light. Finding even one live louse or fresh nit on a pubic hair confirms an active infestation CDC DPDx.
Preventing crabs from coming back
Breaking the cycle takes coordinated timing across the medicine, your partner, and your laundry. Do all three on the same day.
- Finish the full treatment course, including the repeat dose. Apply an over-the-counter 1% permethrin lotion or a pyrethrins-with-piperonyl-butoxide mousse to all affected coarse hair, then repeat in 9–10 days if live lice remain. Don't stop just because the itch eased; the repeat dose catches lice that hatched from surviving eggs. Full steps are covered in how to get rid of crabs at home.
- Treat partners simultaneously. Everyone with skin contact in the past month should be treated at the same time, even if they have no symptoms yet. Wait until both partners finish before resuming sex.
- Hot-wash and dry the right items. Machine-wash bedding, towels, and clothing used in the prior two to three days in hot water and dry on high heat. Items you can't wash can be sealed in a plastic bag for a couple of weeks.
- Don't use insecticide on eyelashes. If lice reach the lashes, treat with ophthalmic-grade petrolatum (not regular Vaseline), never lice shampoo near the eyes.
- Lower future risk. Condoms used every time reduce transmission of the sexually transmitted infections, and routine testing catches the ones that produce no symptoms. Crabs themselves can spread despite a condom because they live on hair the condom doesn't cover, so treating your partner does the work barrier protection can't.
When to retest
There's no blood test for crabs; the "retest" is a careful re-inspection. After your repeat treatment, check the pubic and perianal hair for live, moving lice. No live lice means the infestation is cleared, even if a few empty nit shells stay stuck to old hair. If you find live lice after completing both applications, involve a clinician rather than re-dosing on your own.
Separately, because pubic lice signal recent sexual contact, this is a logical time for a broader sexual-health check. If you're weighing options, you can compare testing providers before you decide where to go.
When to see a clinician
Self-treatment handles most cases, but talk to a clinician if any of the following applies:
- You still find live lice after completing the full course, including the repeat application.
- Lice involve the eyelashes or eyebrows, which need a different, eye-safe treatment.
- The skin where you applied the medicine becomes badly inflamed, oozing, or infected from scratching.
- You're pregnant, breastfeeding, or treating a young child — product choice may differ.
- You want testing for other sexually transmitted infections, since crabs often travel with infections that have no symptoms.