Before we begin, let's get one thing out of the way first: Your vagina is supposed to have a smell, despite what rude sexual partners or all those companies that make weird crotch perfumes may have told you in the past. In fact, healthy vaginas emit a full Sephora's worth of different scents throughout the month, with stronger and more subtle variations of your unique smell appearing during different parts of your menstrual cycle. Some people naturally emit stronger vaginal odors, while others don't. And our vaginal odor can be altered when we sweat, or if semen or other bodily fluids come into contact with it (scientific terminology: "Gettin' love goo all up in there"). But make no mistake: Your vagina has a scent, always.

"Vaginal odors are very common, and may be due to an imbalance of the 'good guy' and 'bad guy' bacteria of the vagina," Dr. Mary Jane Minkin, a clinical professor in the Department of Obstetrics, Gynecology, and Reproductive Sciences at the Yale University School of Medicine, tells Bustle. Good guy bacteria are strains like lactobacillus, which help keep your vagina at a naturally acidic level, while things like candida are a bad guy, so to speak, since they overgrow if not kept in check by lactobacillus.

While a scent is a sign that your junk is healthy and has its pH properly balanced, a change in smell can sometimes be a sign that there's trouble, right here in Vagina City. Sometimes, an unusual odor coming from your vagina can signal a health problem, like a lost tampon or bacterial vaginosis infection. Other times, it may simply mean that you've just finished up your period, or some other totally healthy and common occurrence.

So how do you tell the difference between an OK change in vaginal scent, and one that means you might have a problem? The only way to get a handle on the way your vagina smells when it's unhealthy is to get very familiar with how it smells when it's healthy, so that you have a baseline for what's normal for you and what isn't.

But even if you haven't put in hours cataloging your own vaginal smells, there are still times when you can tell that your vagina smells a bit off. So when do you need to see a doctor, and when do you just need to switch to all-cotton underpants? Read on and take a whiff, friends.

1. Fishy Scent

Could it mean that something's off? Yes.

The idea that vaginas "smell like fish" is used so often to put them down, it's almost hard to talk about the times when this particular vaginal odor can signal a real medical problem. But an intense fishy smell in your deep blue sea can be a sign of two common vaginal infections: bacterial vaginosis and trichomoniasis.

According to the Mayo Clinic, bacterial vaginosis is a "vaginal inflammation caused by the overgrowth of bacteria naturally found in the vagina." It is not an STI, though it often occurs after sex with a new partner. Other symptoms besides a fishy smell include itching, gray or white discharge, or even burning during urination — symptoms similar to a number of STIs, so make sure to get checked out by a doctor to confirm what's actually going on.

Trichomoniasis is the most common curable STI in America — according to the CDC, 3.7 million people have it. Symptoms include the aforementioned fishy smell, itching on and discharge from genitals, and pain while urinating — though 70% of cases don't have any symptoms.

Both infections can be cleared up easily with a course of prescription antibiotics, so don't hesitate to see your OB/GYN.

2. Metallic Scent

Could it mean that something's off? Probably not (but on occasion, yes).

A metallic scent coming off your vag is most common right before, during, and after you've had your period. This is the smell of your period blood, and totally normal.

You might also get a whiff of a metal-esque scent if you've recently had penetrative vaginal sex — sex with someone who ejaculates can change the pH in your vagina, because semen is naturally alkaline. This is, again, very normal.

However, if the smell persists long after your period is gone/ long after your rendezvous, check in with your doctor — especially if it is accompanied by any itching or discharge.

3. Yeasty Scent

Could it mean that something's off? Possibly.

According to the Mayo Clinic, yeast infections don't give off any scent at all most of the time, and so you'll have to recognize them from their other symptoms (like the dreaded thick white discharge and itchiness).

But some experts believe that in some cases, your yeastified bits might emit a faint odor, one that can smell slightly yeasty. However, smell will never be your only symptom with a yeast infection, so keep your eyes open — and don't hesitate to contact a doctor to help you figure it out, especially if you've never had one before.

4. Musky Scent

Could it mean that something's off? Probably not.

A musky scent that smells just like a heavier version of your vagina's usual scent typically means that you've been sweating a lot — in fact, you actually have a sweat gland in your genital area (cool??). Washing your funky bunch (of vulva) with some mild, unscented soap and changing out of your skinny jeans every once in a while should fix things up if you find this scent a little to strong for your tastes. But know that this doesn't signify that anything is medically wrong.

5. Rotten Scent

Could it mean that something's off? Yes.

If your vagina suddenly takes on an intense rotten smell, get in touch with your OB/GYN immediately. It's definitely not healthy, and could be a sign of a tampon gone astray in your vagina during your last period, which is way, way, way more common than you think. Your doctor has definitely dealt with extracting a long-forgotten tampon before, so don't be shy about setting up an appointment.

In fact, don't be shy about booking an appointment with your doc about any of these issues. These are all really run-of-the-mill gynecological problems, and your doctor won't be disgusted with you or think you have bad hygiene if you come in with a concerning vagina smell. Your OB/GYN is a licensed medical doctor, which means that they TOUCHED CORPSES in medical school, OK? They had to spend years doing internships and residencies where they dealt with every manner of gross, horrifying ailment, and they have become desensitized to all of it.

So please don't be nervous about reaching out to a medical professional. There is literally nothing that could go wrong with your vagina that could shock them — and even if there was, your health is too important.

Additional reporting by Syeda Saad.

Studies referenced:

Miller, E. A., Beasley, D. E., Dunn, R. R., & Archie, E. A. (2016). Lactobacilli Dominance and Vaginal pH: Why Is the Human Vaginal Microbiome Unique?. Frontiers in microbiology, 7, 1936. doi:10.3389/fmicb.2016.01936

Experts:

Dr. Mary Jane Minkin, MD, OB/GYN, clinical professor at the Yale University School of Medicine