Crabs and scabies both itch in the genital area, but they're different parasites with different treatments. Crabs (pubic lice) are visible insects that cling to coarse hair. Scabies is a microscopic mite that burrows into skin and itches worse at night. Lice are picked off; scabies needs a whole-body scabicide. A clinician's exam settles it.
mite; permethrin or ivermectin
treatable; topical
| Item | Value |
|---|---|
| Scabies | curable — mite; permethrin or ivermectin |
| Pubic lice (crabs) | curable — treatable; topical |
What each one is
Scabies
Scabies is an infestation by the human itch mite, Sarcoptes scabiei, a microscopic mite that tunnels into the upper layer of skin to live and lay its eggs CDC. It's found worldwide, and in adults it spreads readily during prolonged skin-to-skin contact, including sex. The itch and rash aren't caused by the bite. They're an allergic reaction your immune system mounts against the mites, their eggs, and their waste, which can take weeks to build.
Pubic lice (crabs)
Pubic lice are Pthirus pubis, blood-feeding insects roughly the size of a pinhead that grip onto coarse body hair, mainly the pubic and perianal hair, and sometimes the armpits, chest, beard, or eyelashes CDC. Their crab-like front claws are built to clasp thick hair shafts, so they don't usually colonize scalp hair. They spread mostly through sexual contact. Unlike scabies, the lice and their eggs sit on the hair where you can often see them — you can read more in our overview of crabs symptoms.
Symptoms compared
Both can cause genital itching, which is why people confuse them. The patterns differ in useful ways.
Scabies brings intense itching that's classically worse at night, plus a pimple-like rash and, sometimes, tiny raised crooked lines where the mite digs its burrows CDC. It favors the webs between the fingers, the wrists, and the waist, buttocks, and penis. After a first infestation, symptoms typically take four to eight weeks to appear, and an infected person can pass it on before noticing anything. If you've had it before, symptoms can show up much faster on a repeat exposure.
Pubic lice often cause no symptoms at all. When they do, it's itching in the genital area, sometimes worsened by an allergic response to the bites, plus visible lice or nits (the eggs) cemented to the hair shafts. Scratching can break the skin and lead to sores or a secondary bacterial infection.
How to tell them apart
The most reliable clue is whether you can see the parasite. Pubic lice and their nits are visible to the naked eye on the hair. Scabies mites are microscopic and never visible; what you'd see instead are burrows and rash on the skin.
- Visible bugs or eggs clinging to pubic hair point to crabs.
- Itching that's distinctly worse at night, with thin crooked burrow lines and rash spreading beyond the hairy area, including the finger webs and wrists, points to scabies.
- Crabs stay where coarse hair is. Scabies roams across the skin and commonly hits sites with no hair at all.
- The symptoms overlap enough that you usually can't be sure by feel alone. An exam or test settles it.
Crabs vs scabies at a glance
| Scabies | Pubic lice (crabs) | |
|---|---|---|
| Cause | Sarcoptes scabiei mite (microscopic) | Pthirus pubis louse (visible) |
| Where it lives | Burrows inside the skin | On coarse hair, feeding on blood |
| Typical sites | Finger webs, wrists, waist, buttocks, penis | Pubic and perianal hair; sometimes armpits, chest, beard, eyelashes |
| Hallmark sign | Crooked burrows, night-worse itch | Visible lice or nits on hair |
| Symptom onset | 4–8 weeks after first infestation | Often none; itching if present |
| Confirming test | Clinical exam; skin scraping under microscope | Spotting a louse or nit, often with a magnifier |
| Treatment | Prescription scabicide (whole body) | Over-the-counter lice product (local) |
Testing
Scabies is usually diagnosed clinically, with a clinician recognizing the burrows, rash, and itch pattern CDC. A skin scraping examined under a microscope can confirm mites, eggs, or mite feces, but it's less sensitive than the clinical picture, so a negative scraping doesn't rule scabies out. Pubic lice are diagnosed by finding a louse or its nits on the hair; a magnifying lens helps when they're hard to spot CDC DPDx.
In practice an evaluation is quick: a focused skin exam, and depending on what's suspected, a urine sample or a self-collected swab to check for other infections people are exposed to at the same time. Visits are free or low-cost at health departments, Planned Parenthood, and Title X clinics. Because genital itching can have many causes and exposures often come bundled, it's worth booking a broader get tested visit rather than guessing at one parasite. If you're timing things after a recent contact, our guide on when to test after exposure explains how long different infections take to show up.
Treatment compared
The treatments are not interchangeable. A lice product won't clear scabies, and a scabicide is the wrong delivery for lice on hair.
Scabies needs a prescription scabicide. The standard is permethrin 5% cream applied to the whole body from the neck down and washed off after 8 to 14 hours; oral ivermectin at 200 µg/kg, repeated in 14 days, is an alternative CDC. Because the mite spreads before symptoms, everyone in the household and all sexual and close contacts from the past month should be treated at the same time, or the infestation bounces back. Wash and hot-dry bedding and clothing, or seal items away from skin for 72 hours. Itching can linger for two to four weeks even after the mites are dead; that residual itch is the immune reaction settling down, not treatment failure. Our guide to preventing scabies reinfection covers the contact-treatment and decontamination steps in detail.
Pubic lice respond to an over-the-counter product — a 1% permethrin lotion, or a pyrethrins-with-piperonyl-butoxide mousse — applied to the pubic hair and affected areas, then repeated in 9 to 10 days if live lice remain CDC. Hot-wash and dry anything worn or slept on in the prior two to three days. Lice on the eyelashes are an exception: they're not treated with insecticide but with ophthalmic-grade petrolatum (not regular Vaseline) under medical guidance.
For the full STI treatment context, including how clinicians handle co-infections, the CDC's ectoparasitic infection guidance is the reference standard CDC STI Tx Guidelines.
Can you have more than one at once?
Yes. Scabies and pubic lice are separate organisms, and being infested with one gives you no protection against the other. You can carry both, and either can travel alongside other sexually transmitted infections. Because both spread through the same close contact, finding one is a good reason to screen for the rest. Treating only the parasite you noticed can leave a second problem behind.
When to see a clinician
See a clinician if you have persistent genital itching, a spreading rash, visible bugs or eggs on hair, or sores from scratching. Get checked, too, if over-the-counter lice treatment hasn't worked after a proper repeat application, if itching from treated scabies keeps worsening past a few weeks, or if a partner has been diagnosed. Eyelash involvement and infestations during pregnancy should always be handled with a clinician rather than self-treated.