Why Having Sex with a New Partner Can Mess with Your Vagina In More Ways Than One

Don't be surprised if sex with a new ~friend~ throws your vagina off balance.

While having sex with a new partner can be fun and exciting, it can also be a little nerve-wracking. Turns out, the weirdness isn't just in your head: Sex with a new partner can actually freak out your vagina a bit too. (And we're not talking about STDs.)

It's not anything to worry about—and certainly not a reason to abstain forever. However, maintaining healthy hygiene and knowing what's normal for you down there inside and out (yep, literally) can help you keep tabs on what's happening after a new hookup.

What do you mean, it "freaks out?"

ICYDK, there's a healthy balance of bacteria in your vagina—just like in your gut—and when it comes in contact with an unfamiliar "package," that balance can get thrown off.

"Sex with a new male partner introduces new bacteria (about 10 million bacteria per ml of semen), often resulting in a change of the [vaginal] microbiome," says Kathryn Wells George, M.D., a gynecologist in New York City. This specific number of bacteria is only the case for unprotected sex if a male partner ejaculates inside of you; however, "pre-cum is relevant to throwing off your microbiome since it contains and introduces new bacteria, too," says Dr. George.

This imbalance may then lead to a host of side effects such as a change in pH, odors, bacterial vaginosis (a.k.a. BV, a super common infection), urinary tract infections, yeast infections, burning, and itching.

Most women's vaginas contain a lot of lactobacilli, a natural bacteria that helps produce lactic acid and keep the vaginal pH low (<4.5), at a healthy level. "The low pH aids in preventing the growth of the bacteria that causes BV (Gardnerella) and helps to maintain high levels of lactobacilli, thereby preventing an overgrowth of yeast," she says. That's right: Lactobacilli keep the vaginal pH low, and this low vaginal pH then helps maintain normal levels of lactobacilli by keeping the microbiome in check. (Your vag is basically a happy, little self-sustaining ecosystem.)

Maintaining this balanced ecosystem is what keeps new, outside organisms from growing out of control. Get this: Sometimes HIV and HSV-2 (herpes) can even be inactivated by the low pH, she adds. (Yep, it's that powerful.) Unprotected sex with a new partner, however, can throw off your vaginal pH, which can disrupt your vag's germ-fighting powers and lead to a growth of foreign bacteria. (Related: Why Condoms Are Good for Your Vaginal Health—and Not Just Because of STDs.)

This isn't just a P-in-the-V issue, either: If you're having sex with a new female partner, their vaginal bacteria can throw off your microbiome, too. Plus, there's the same risk of passing bacteria that could lead to infections: "Whether your new partner is a man or woman, the same common infections can occur," says Sherry Ross, M.D., ob-gyn and women's health expert in Santa Monica, CA, and author of She-ology: The Definitive Guide to Women's Intimate Health.

What can you do to prevent it?

Let's face the facts: You're not going to stay celibate for the rest of your life (or—gasp!—go back to an ex) in the name of keeping your vaginal bacteria ~chill~. However, if you find that sleeping with a new partner leaves you with a bunch of annoying symptoms, the good news is that there are things you can do to minimize them. (And, luckily, in a long-term, monogamous relationship, the vaginal microbiome typically remains in a steady state, says Dr. George.)

"Of course, barrier methods, such as condoms, will prevent the introduction of new microorganisms," says Dr. George. (Besides, you really should be using condoms with a new partner, anyway.) Condoms can help limit your exposure to unfriendly bacteria from a new partner—just make sure you go with a non-lubricated one. "Condoms without lubricant will not disrupt the vaginal microbiome, but condoms with lubricant (or lubricant in general) can alter the pH level and make the pH more alkaline, disturbing the microbiome," says Dr. George. Look for lubricants that have a pH matched to the vaginal pH, she says. (Try GoodCleanLove BioNude Personal Lubricant, $12; goodcleanlove.com)

As always, before jumping into bed, it's important to be upfront with a new partner about both parties' sexual history, STD status, and any infections either person may currently have, explains women's health expert Roshini Raj, M.D., an ob-gyn in New York. (And that's just part of having sex safe, period.) Just one example: "A yeast infection can be contagious if your partner has thrush or a yeast infection of the penis," says Dr. Raj. (She also recommends resources like KeepHerAwesome.com to learn more about specific vaginal infections and ways to keep yourself clean and protected.)

Probiotics can help restore a healthy microbiome, says Dr. George. You can take oral probiotics (the same ones that boost your gut health) or vaginal probiotics, which can be taken orally or inserted topically, to directly target the vaginal microbiome. (See: 5 Legit Benefits of Probiotics and How to Take Them.)

Regardless of whether it's a new partner or not, there are some sexual hygiene practices you should always do to keep your vagina balanced:

• Peeing or washing your vagina with water after sex can help cleanse the vagina and keep bacteria balanced. Just don't douche, which can further upset the vagina's pH levels and bacteria. "I also always tell my patients to refrain from using scented soaps and douching. Plain water typically suffices to clean your vulva, but if you prefer to use a soap, make sure it's gentle and unscented," says Dr. Raj. (Related: Why You Don't Need to Clean (Or Buy Fancy Things for) Your Vagina)
• Refrain from sex if you cut yourself shaving. "The skin in your vagina is very sensitive and if you have any sort of cut it can lead to irritation or risk of STIs," she says. "It's best to avoid having sex until it's fully healed because an open cut will allow for bacteria to enter your bloodstream," she explains.
• Bring your own condom. "The majority of condoms are made out of latex," says Dr. Ross. "A small percentage of women have a latex allergy which can cause vaginal swelling, itching, and pain during sex." If you experience any of these symptoms after sex with a condom, you may be allergic. Try using polyurethane condoms as an alternative for safe sex, she says.
• Wash your hands before and after sex. "Bacteria from the fingers, mouth, and rectum can increase your chance of developing a yeast or bacterial infection. Hands and fingers need special attention before being sexually active. Your hands and fingers are overwhelmingly dirty with unwelcomed bacteria," says Dr. Ross. "One of the most common bacteria found on your hands and fingers is E.coli, which comes from fecal (poop!) matter. If E.Coli is passed into the vagina it can cause a vaginal or urinary tract infection," she says.

Something's definitely off... now what?

"If you find yourself with non-STD vaginal symptoms after sex with a new partner, such as a yellow-green discharge with foul odor, it may be BV," says Dr. George. "There are both at-home remedies and prescription treatments," she says, so as long as you spot the symptoms, the infection will clear up pretty quickly.

It can also be a yeast infection, which looks a bit different. "Yeast infections will present with a thick, white, cottage cheese-like discharge typically with itching and/or burning," says Dr. George. "Treatments for yeast infections include at home remedies, over-the-counter medications, and prescriptions," she says. Again, super easy to treat. (Here's how to decode your vaginal odor and the color of your vaginal discharge.)

Lastly, you might experience a UTI. "UTIs will typically present with painful and frequent urination and require prompt medical evaluation to prevent a kidney infection," she says.

If you don't have an infection, you could still notice some signs signaling that something's off down there. "If it is not a discharge that is green and foul-smelling (BV), and if it is not white and cottage cheese like, causing itching and burning, (yeast), and if there are no signs of an STD, it may be that you need to wait for a [menstrual] cycle or wait a few weeks to see if your microbiome recorrects itself," says Dr. George. If you think it could be an STD or symptoms don't go away after a few weeks, speak to your ob-gyn for more suggestions for treatment.

The good news: If you do notice some weirdness after sex with someone new, you're not allergic or doomed. Your magical, self-cleaning vagina (maybe with the help of some probiotics) will likely sort itself out and adapt to your new partner naturally.