Crabs is the common name for pubic lice, tiny parasitic insects that live in coarse body hair, most often in the genital area. They spread primarily through skin-to-skin sexual contact and cause intense itching. While not dangerous, they’re a nuisance that requires treatment to eliminate.
What Pubic Lice Actually Are
Pubic lice are a distinct species of louse, separate from head lice or body lice. They get the nickname “crabs” because of their shape: they’re broader and flatter than other lice, with large front claws that make them look like tiny crabs under magnification. Adults are only about 1.1 to 1.8 mm long, roughly the size of a pencil tip, so they’re difficult to see with the naked eye but not invisible.
These insects feed on human blood and spend their entire life cycle on the body. A female lays around 30 eggs (called nits) over her 3 to 4 week lifespan, gluing them to the base of hair shafts. Eggs hatch after about a week, producing nymphs that go through three molts before becoming adults capable of reproducing. This cycle matters for treatment, because killing the adults alone won’t solve the problem if eggs remain.
Pubic lice are extremely sedentary. Unlike head lice, they rarely move from one hair to another and stay in close contact with the skin almost constantly. They’re most commonly found in pubic hair but can also infest other coarse body hair, including chest hair, armpit hair, beards, eyebrows, and eyelashes.
How Crabs Spread
Close intimate contact, specifically skin-to-skin contact, is the primary route of transmission. This is why pubic lice are classified alongside other sexually transmitted infections. Because the lice are so sedentary and rarely leave the body, transmission through shared clothing, towels, or bedding is highly unlikely. It’s theoretically possible but not a realistic concern for most people.
Having pubic lice has also been associated with other sexually transmitted infections. If you’re diagnosed with crabs, it’s worth getting tested for other STIs as well, since the same type of contact that transmits lice can transmit other infections.
Symptoms to Look For
The hallmark symptom is itching in the genital area, which can range from mild to intense. The itch comes from your body’s allergic reaction to louse saliva, which the insects inject while feeding. If you’ve never had pubic lice before, it can take several days to a few weeks after infestation for the itching to start, because your immune system needs time to develop that allergic response. A repeat infestation tends to cause itching much sooner.
Other signs include:
- Visible nits: Tiny oval eggs attached firmly to hair shafts near the skin, often yellowish-white
- Crawling lice: Small grayish-white or tan insects at the base of hairs, sometimes with a reddish tint after feeding
- Blue-gray spots: Small discolorations on the skin called maculae ceruleae, caused by a reaction to louse bites
- Dark specks on underwear: These are louse droppings
Excessive scratching can break the skin and lead to secondary bacterial infections, which may cause redness, swelling, or crusting beyond what the lice alone would produce.
How Crabs Are Treated
Pubic lice are treatable with over-the-counter topical products. The two most common options are permethrin lotion (1%) and pyrethrin-based products. Both work by killing the lice on contact. You apply the product to the affected area, leave it on for the directed time, then rinse it off.
Because these products don’t reliably kill eggs, a second treatment is typically needed 7 to 10 days later. This catches any nymphs that hatched from surviving eggs before they’re old enough to lay new eggs themselves. If you still see live, crawling lice a week after your first treatment, that’s your signal to retreat.
One complication: resistance to these standard treatments has been increasing and is now widespread. If an over-the-counter product doesn’t work after two applications, a doctor can prescribe stronger alternatives. Oral medication is one option, as are prescription-strength topical treatments that work through a different mechanism than the OTC products.
If lice have spread to your eyelashes or eyebrows, standard insecticidal treatments can’t be used near the eyes. A doctor will need to recommend a safe alternative for those areas, often a petroleum-based ointment that suffocates the lice.
Cleaning Your Home After Treatment
Pubic lice can’t survive long away from a human host, but it’s still smart to clean items you’ve used in the 2 to 3 days before treatment. Machine-wash clothing, towels, and bedding in hot water (at least 130°F) and dry them on the hot cycle. Items that can’t be washed can be sealed in a plastic bag for two weeks, which is long enough for any lice or eggs to die without a blood meal.
You don’t need to fumigate your home or treat furniture extensively. Since pubic lice are so dependent on close body contact, environmental contamination is minimal. Focus your cleaning efforts on fabrics that had direct contact with your body.
Sexual Partners and Reinfestation
Any sexual partners from the past month should be notified and treated at the same time, even if they don’t have symptoms yet. If your partner isn’t treated, you’ll simply pass the lice back and forth. Avoid sexual contact until both you and your partner have completed treatment and confirmed the lice are gone.
A successful treatment means no live lice visible after 7 to 10 days. Nits glued to hair shafts may remain visible for a while after treatment, but dead nits don’t indicate an active infestation. The key indicator is whether you see anything moving.