The most obvious sign of crabs (pubic lice) is persistent itching in the genital area that doesn’t go away. This itching can start within days of exposure or take up to 2 to 4 weeks to appear, which means you could be infested for a while before noticing anything. The itch comes from an allergic reaction to lice bites, and it tends to get worse at night when the lice are most active.
What Itching From Crabs Feels Like
The itching from pubic lice is different from a yeast infection or jock itch. It’s concentrated in areas with coarse hair, primarily the pubic region, but potentially the inner thighs, armpits, chest hair, or even facial hair like beards and mustaches. The itch is relentless and gets worse over days rather than better. Scratching provides only brief relief before the urge returns.
Because the itching can take weeks to develop after initial exposure, many people don’t connect it to a specific sexual encounter. If you’ve had intimate contact with someone in the past month and develop unexplained genital itching, crabs are worth checking for.
What to Look For on Your Body
The surest way to confirm crabs is finding the lice themselves or their eggs. Pubic lice are tiny, roughly 1 to 2 millimeters long, and have a distinctive crab-like shape with wide bodies and large front claws that grip hair shafts. They’re tan to grayish-white and can be hard to spot because they stay very still once attached to a hair.
Eggs (called nits) are even smaller, oval-shaped, and yellowish-white. They’re glued firmly to the base of hair shafts, close to the skin. Unlike dandruff or dry skin flakes, nits don’t brush off easily. If you try to slide something along the hair and it stays stuck, that’s a strong indicator. A magnifying glass and good lighting help enormously, since these are easy to miss with the naked eye.
You may also notice tiny dark or rust-colored specks in your underwear. These are lice droppings, which is another reliable sign.
Blue-Gray Spots on the Skin
Some people develop small blue or slate-gray spots on the inner thighs, lower abdomen, or groin area. These painless marks are caused by a substance in lice saliva that interferes with normal blood clotting at the bite site. Not everyone gets them, but if you notice unexplained bluish discoloration in these areas alongside itching, it’s a distinctive clue that points specifically to lice rather than other skin conditions.
Where Crabs Can Spread Beyond the Groin
Pubic lice prefer coarse body hair, not the finer hair on your head. While they’re most common in the pubic region, they can also show up on the perianal area, armpits, chest, abdomen, mustache, beard, and even eyelashes or eyebrows. If you find lice or nits in any of these areas, it’s the same infestation. Eyelash involvement is more common in children who’ve been in close contact with an infested adult, and it can cause eye irritation and redness.
How You Get Crabs
Pubic lice spread almost exclusively through intimate, skin-to-skin contact, usually during sex. The lice crawl from one person’s body hair to another’s. They cannot jump or fly.
Spread through shared clothing, towels, or bedding is possible but uncommon. Toilet seats are an even rarer route. Adult lice need human blood to survive and die within 24 to 48 hours once separated from a host, so they don’t linger long on surfaces. Still, if you’re treating an infestation, washing bedding and recently worn clothing is a smart precaution.
How Diagnosis Works
Diagnosis is straightforward: a healthcare provider looks at the affected area for moving lice or nits attached to hair shafts. Seeing a live louse confirms the diagnosis. No blood test or swab is needed. Many people can actually confirm it themselves at home with a magnifying glass, though a provider visit is helpful for distinguishing crabs from other conditions that cause genital itching, like eczema, folliculitis, or scabies.
Treatment Options
First-line treatment is a permethrin 1% lotion or a pyrethrin-based shampoo, both available over the counter. You apply the product to all affected areas, leave it on for the recommended time (usually 10 minutes), and rinse. A second application about 9 to 10 days later catches any lice that hatched from surviving nits after the first round.
Over-the-counter permethrin clears the infestation in 50% to 97% of people within two weeks. If it doesn’t work, prescription alternatives are available, including malathion lotion (about 80% effective at 14 days) or oral ivermectin, which clears 92% to 97% of cases after two doses. Your provider can guide you if the OTC option fails.
During treatment, avoid sexual contact until you and any partners have completed the full course. Wash all clothing, towels, and bedding used in the two days before treatment in hot water and dry on high heat. Items that can’t be washed can be sealed in a plastic bag for two weeks, which starves any remaining lice.
Complications From Scratching
Crabs themselves don’t transmit diseases, but intense scratching can break the skin and open the door to bacterial infections. If the affected area becomes red, swollen, warm to the touch, or starts oozing, that suggests a secondary skin infection that may need separate treatment. Keeping your nails short and resisting the urge to scratch reduces this risk while you wait for treatment to work.
Why Partners Need Treatment Too
Anyone you’ve had sexual contact with in the past month should be notified and treated, even if they have no symptoms yet. Remember, itching can take up to four weeks to start. If only one partner is treated, the lice simply pass back and forth. Both people need to complete treatment before resuming intimate contact.