The main complications of pubic lice come not from the insects themselves but from what scratching does to the skin. Persistent itching breaks the skin, opening the door to secondary bacterial infection. Less commonly, lice on the eyelashes cause irritation and conjunctivitis. Crabs don't transmit other diseases, and treatment clears both the lice and most complications.
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 |
The essentials: why crabs cause problems at all
Pubic lice are Pthirus pubis, small insects that feed on blood and live mainly in coarse pubic and perianal hair, and sometimes in the armpits, chest, beard, or eyelashes CDC DPDx. They spread mostly through close sexual contact. The lice themselves are not dangerous. They don't burrow, they don't spread through the bloodstream, and they're not known to carry other infections. When people talk about "crabs complications," they almost always mean the downstream effects of the itch and the scratching it provokes, plus the special case of lice that settle on the lashes.
Most infestations cause no symptoms at all CDC, About Pubic Lice. When they do, the hallmark is itching in the genital area, often worse at night when the lice are most active. The itch is an allergic-type reaction to louse saliva injected when they feed, which is why it can take a week or two to build after a new exposure. If you're not sure what you're looking at, our guide on what pubic lice look like shows the difference between an adult louse and a nit (egg) glued to the hair shaft.
Symptoms and complications to watch for
Secondary bacterial infection from scratching
This is the most common complication. Intense, repeated scratching tears the surface of the skin, and the bacteria that normally live harmlessly on the body — staph and strep species — get into those breaks. The result can be impetigo (a crusted, oozing surface infection), folliculitis (infected hair follicles that look like small pus-filled bumps), or, in deeper cases, cellulitis (a spreading infection of the skin and the tissue beneath it that makes the area red, hot, swollen, and tender). Signs that a scratch has turned into an infection include increasing redness, warmth, pain, yellow crusting or pus, and sometimes fever. The pubic and groin area is warm and moist, a forgiving environment for bacteria, so any worsening after a few days of itching deserves attention.
Maculae ceruleae (blue spots)
Some people develop small, slate-blue or grayish spots on the skin of the lower abdomen, thighs, or buttocks. These are bruise-like marks thought to come from the lice feeding and from pigment changes at the bite sites. They're harmless and fade on their own once the infestation is treated, but they can be alarming if you don't know what they are.
Eyelash infestation and conjunctivitis
Pubic lice can occasionally settle on the eyelashes, a condition clinicians call pthiriasis palpebrarum, and one of the more uncomfortable complications. Lice and nits clinging to the lash line irritate the eye and can cause conjunctivitis (inflammation of the membrane covering the white of the eye), with redness, a gritty or itchy feeling, tearing, and crusting along the lid margins. In children, lashes are a recognized site, and finding lice there should prompt a careful, non-judgmental conversation about how the exposure happened. Eyelash infestation is never treated with the insecticide lotions used elsewhere on the body, because those products can damage the eye.
Reinfestation and the ping-pong problem
The most frustrating "complication" is simply getting crabs again. This happens when a partner isn't treated at the same time, when live lice survive a first treatment, or when contaminated bedding and clothing reintroduce them. It usually means the cycle wasn't closed, not that the medicine failed.
How crabs are diagnosed
Diagnosis is straightforward and doesn't require a lab. A clinician, or you at home, finds an adult crab louse or its nits attached to hair in the pubic region. The lice are visible to the naked eye, though a magnifying lens makes the squat, crab-shaped body and the firmly glued eggs much easier to confirm. There's no blood test or swab for crabs the way there is for other infections; it's a visual diagnosis. If you want to walk through the inspection step by step, see how to test & diagnose crabs at home.
Because crabs are sexually transmitted, finding them is a reasonable cue to check for other infections that often travel together and frequently cause no symptoms. Most 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 new partner, it's worth knowing when to test after exposure so you don't test too early, and you can get tested at the same visit.
Treatment — clearing the lice and the complications
First-line treatment is an over-the-counter lice product: a 1% permethrin lotion or a pyrethrins-with-piperonyl-butoxide mousse, applied to the pubic hair and affected areas, then washed off as directed CDC, Pubic Lice Treatment. If live lice are still present afterward, the treatment is repeated in 9–10 days to catch any that hatched from surviving eggs. Hot-wash and machine-dry on high heat any bedding, towels, and clothing used in the prior 2–3 days; items that can't be washed can be sealed away. Follow the product instructions fully even once the itching eases, since stopping early is a common reason crabs come back.
Eyelash infestations are handled differently. Lashes are treated with an ophthalmic-grade petrolatum applied to the lid margins, not regular Vaseline, and never an insecticide lotion. The petrolatum smothers the lice over several days, and a clinician may remove visible lice and nits from the lashes directly.
Treating the complications follows the standard logic: a secondary bacterial infection like impetigo or cellulitis needs its own antibiotic treatment from a clinician, separate from the lice medicine, and lash-related conjunctivitis improves once the lice are cleared. According to the STI treatment guidelines, the priority is killing the lice, treating partners, and decontaminating the environment so the cycle ends CDC STI Tx Guidelines.
| Situation | What's used | Key detail |
|---|---|---|
| Pubic / body hair | 1% permethrin lotion or pyrethrins-with-piperonyl-butoxide mousse | Repeat in 9–10 days if live lice remain |
| Eyelashes | Ophthalmic-grade petrolatum | No insecticide near the eyes; not regular Vaseline |
| Secondary skin infection | Clinician-prescribed antibiotic | Treated separately from the lice |
| Bedding & clothing | Hot wash + high-heat dry | Items used in the prior 2–3 days |
Preventing complications and reinfestation
Most complications are avoidable by treating early and treating everyone involved. The core steps:
- Tell all sex partners from the past month so they can be treated at the same time, and avoid sexual contact until both partners are treated.
- Decontaminate bedding and clothing alongside treatment so lice aren't reintroduced.
- Resist scratching as much as possible, since scratching causes most skin infections; trimming nails and treating promptly cuts the urge.
- Don't share towels or bedding while a household member is being treated.
- Used every time, condoms lower the risk of the sexually transmitted infections crabs often travel with, and routine testing catches what has no symptoms.
For the full playbook on closing the cycle, see how to prevent crabs & avoid reinfestation.
When to see a clinician
Over-the-counter treatment handles most cases at home, but see a clinician if the area becomes increasingly red, warm, swollen, or painful, if there's pus or yellow crusting, or if you develop a fever, which point to a secondary bacterial infection that needs antibiotics. Get medical care for any lice on the eyelashes, especially with red, irritated, or watering eyes, since the eye area shouldn't be self-treated with lice products. You should also check in if live lice persist after repeating treatment, if you're pregnant or breastfeeding, or if the patient is a child. A diagnosis of crabs is common and treatable. Clinics handle it daily, and it says nothing about you as a person.