Yes, crabs are classified as a sexually transmitted infection. “Crabs” is the common name for pubic lice, tiny parasites that cling to coarse body hair, most often in the genital area. The CDC includes pubic lice in its official Sexually Transmitted Infections Treatment Guidelines because sexual contact is the primary way they spread. That said, crabs are parasitic insects, not a bacterial or viral infection, which makes them different from most STIs in important ways.
How Crabs Spread
Pubic lice pass from person to person mainly through close, skin-to-skin contact during sex. The lice crawl from one person’s body hair to another’s. They cannot jump or fly.
Less commonly, crabs can spread through shared clothing, bedding, or towels. Transmission from a toilet seat is technically possible but extremely rare, since lice can only survive about one to two days away from a human body. Condoms do not reliably prevent transmission because the lice live in hair and skin that condoms don’t cover.
What Crabs Feel Like
The hallmark symptom is itching in the pubic area, caused by an allergic reaction to lice bites. This itching can start within days of exposure or take as long as two to four weeks to appear, which means you can carry and spread lice before you notice anything wrong. The itch tends to be worst at night.
If you look closely, you may see the lice themselves. They’re very small (about the size of a pinhead), tan or grayish-white, and shaped somewhat like a miniature crab, which is where the nickname comes from. You might also spot tiny oval eggs (called nits) attached to hair shafts near the skin. Some people develop small bluish spots at bite sites, a reaction to compounds in the lice’s saliva. Persistent scratching can break the skin and lead to secondary bacterial infections.
Although pubic hair is the most common location, crabs can also infest other areas with coarse hair: legs, armpits, chest, facial hair, and even eyebrows or eyelashes.
How Crabs Differ From Other STIs
Unlike chlamydia, gonorrhea, or herpes, crabs are caused by an external parasite rather than a pathogen that enters your body. This distinction matters practically: crabs don’t cause internal damage, don’t affect your immune system, and are curable with a single course of topical treatment. There’s no blood test involved. You can often diagnose them yourself by spotting lice or nits in your body hair.
Another key difference is that crabs don’t always require a doctor’s visit. Over-the-counter treatments are available and effective for most cases.
Treatment
You can treat pubic lice at home with a lice-killing lotion or mousse available without a prescription at any pharmacy. The two main options contain either 1% permethrin or a combination of pyrethrins and piperonyl butoxide. The process is straightforward:
- Wash and dry the affected area first.
- Apply the product thoroughly to all infested hair, leave it on for the time specified on the label, then rinse or remove as directed.
- Check again in 9 to 10 days. If you find live lice, repeat the treatment.
If crabs have spread to your eyelashes or eyebrows, treatment is different. You can carefully remove individual lice and nits with your fingernails or a fine-toothed comb. For heavier infestations in that area, a prescription ophthalmic-grade petrolatum ointment applied to the eyelid margins two to four times daily for 10 days is the standard approach. Don’t use regular petroleum jelly near your eyes, as it can cause irritation.
Cleaning Your Home and Belongings
Lice and their eggs can survive briefly on fabrics, so you’ll want to decontaminate your environment at the same time you treat your body. Wash all clothing, bedding, and towels in hot water (at least 130°F) and dry them on the hot cycle. Anything that can’t be washed should be sealed in a plastic bag for two weeks, which is long enough for any surviving lice or eggs to die. Furniture and mattresses don’t typically need special treatment beyond vacuuming.
Telling Partners
Because crabs spread so easily through sexual contact, anyone you’ve been intimate with recently should know. Sexual partners need to be treated at the same time you are, even if they haven’t noticed symptoms yet. If both of you aren’t treated simultaneously, you’ll simply pass the lice back and forth. Avoid sexual contact and sharing bedding until treatment is complete for everyone involved.
Why Condoms Don’t Help
This catches many people off guard. Condoms protect against infections transmitted through bodily fluids, but pubic lice live on hair and skin across the entire genital region. A condom covers only a small portion of that area. The only reliable way to avoid crabs is to limit skin-to-skin contact with someone who has an active infestation, which is difficult when neither person knows the lice are there. Checking for visible lice or nits before intimate contact can reduce risk, but it’s not foolproof given how small they are.