If things start to itch down there, you could have a bad case of this STD.

Sure, you may have gotten head lice once or twice when you were a kid, but pubic lice or crabs? That's a whole other story. (Needless to say, having an itchy scalp is way less embarrassing than being super itchy down there.)

Getting pubic lice is super common. About 3 million people in the U.S. get pubic lice each year, according to Planned Parenthood. Luckily, it's not dangerous or hard to get rid of.

Here's how to know if that itching means you have something to worry about, and your treatment game plan if it is indeed crabs. (And remember: If things feel off down there, going to see your doc ASAP is always a good idea.)

What are crabs and how do they spread?

Let's get one thing straight: Crabs and pubic lice are the same thing. They're little parasites that usually attach to the skin and hair near your genitals.

"Pubic lice or crabs live in pubic hair and can move from one person's hair to another, especially during sex," says Anita Petruzzelli, M.D., an ob-gyn at BodyLogicMD in Hartford, CT. However, this infection isn't always sexually transmitted: "Occasionally they can be spread by close contact with towels or bed linen from an infected person," says Dr. Petruzzelli. So if you're living with someone with crabs, be extra careful until it's treated. (And do a load of laundry in hot water.)

The good news: It's a myth that crabs can be contracted from a toilet seat-it's totally false. "Because they like to live in human hair and feed on blood, they don't spread by casual touching or stick to hard surfaces like a toilet," says Dr. Petruzzelli. "They also don't live for long when they're not attached to the human body."

Crabs aren't a sign of bad hygiene or uncleanliness, according to Planned Parenthood. It just means you've had contact with someone who has them.

What are the symptoms of crabs?

Pubic lice feed on blood from the genital area, and their bites cause intense itching. You may also see dark spots on the skin from the bites, says Dr. Petruzzelli. (Also see: Why Is My Butt Itchy?)

"[Itching] occurs mainly in the genitals but it can be in any hair-bearing area," says Alyse Kelly-Jones, M.D., an ob-gyn at Novant Health. That means beards, chest hair, armpits, etc., are fair game too-although crabs don't usually hang out on your head. "Groin lymph nodes can be swollen too," says Dr. Kelly-Jones.

However, these symptoms can usually be mistaken for something else, like a rash. (Related: The Truth About Those Below-the-Belt Skin Conditions, Bumps, and Rashes) So how do you know if it's pubic lice?

That's the freaky part: If you have crabs, you may be able to see very tiny small bugs in the pubic area with a magnifying glass. Yikes.

"Pubic lice look like little crabs, hence the name 'crabs,'" says Dr. Petruzzelli. "They have six legs and the front two legs are larger like a crab's. The adult is 1 to 2mm in length and tan or gray color. They are found attached to pubic hair."

Even more unsettling news? They can have babies. "Nits are the eggs laid by the adult. They're very tiny and hard to see," says Dr. Petruzzelli. "They can be found on the bottom part of pubic hairs and may be oval and yellow, white, or pearly in color. When the eggs or nits hatch, they are small and are called a nymph." Keep an eye out for these little eggs in addition to adult crabs. (FYI, not all STDs make themselves this well-known. In fact, these sleeper STDs don't have any symptoms.)

How do you treat crabs?

Don't worry-although having crabs is zero fun, it's easily handled. (That's really good news because, ICYMI, other STDs like gonorrhea and chlamydia might soon be untreatable.)

"Pubic lice are treated with topical lotions or creams like permethrin (Nix, Rid) or pyrethrin," says Dr. Kelly-Jones. They're available over the counter at most drugstores, so you don't need a prescription. "Carefully following the directions on the product will lead to better success," she says, but a second treatment may be needed seven to 10 days later if all the eggs weren't effectively killed.

Once you seek treatment, you can breathe easy. "Pubic lice or crabs are not dangerous because they do not spread disease," says Dr. Petruzzelli. "However, they are uncomfortable, contagious (with close or sexual contact), and can cause infection (if you scratch and the raw skin gets infected)," she says, so you'll want to treat it appropriately and see a doctor as soon as possible if you think something's up.

What's more, make sure your partner is safe, too. "It's important to make sure your sexual partner is also treated at the same time so you don't pass crabs back and forth," she says. And once you've treated your body, clean everything. "It's also important to clean any personal items that could be contaminated such as towels, clothes, and bedding with hot water and dry in a hot air cycle," she says.