Whether you’ve just completed a gruelling workout or chowed down on some onion in your burger or salad, chances are at some point, you’ve been that guy who stunk up the room. In most cases, a simple shower, swipe of deodorant, or line of minty-fresh toothpaste could remedy the situation. But in other cases, it’s not so simple.

That’s because your body odour can actually speak volumes about your health. In fact, some diseases can actually produce a unique, distinguished odour, according to a recent Swedish study.

So which funky fumes should you take note of? Here are 5 common body odours that might signal a serious problem—and what you should do if the stench arises.

1. Bad breathe is a symptom of sleep apnoea

If your morning breath is consistently ripe—even if you brush your teeth regularly—you could be dealing with undiagnosed sleep apnoea, a disorder that causes your breathing to sporadically stop and start while you sleep.

Sleep apnoea can lead to excessive snoring, causing you to breathe through your mouth throughout the night. This can make your mouth very dry, which is a common cause of bad breath, says Raj Dasgupta, M.D., assistant professor of clinical medicine at the University of Southern California.

This allows bacteria to breed more readily—and when certain kinds multiply, they produce a sulphurous gas that can give your breath a rotten egg smell. If you’ve ruled out other causes of bad breath, but still wake up with a smelly mouth and you suffer from daytime sleepiness and snoring, schedule an appointment with your doctor. The sleeping condition has been strongly associated with diabetes, high blood pressure, and heart disease, so treating it sooner than later can spare you of its long-term health effects, Dr. Dasgupta says.

Once you’re diagnosed, your sleep doctor can recommend a continuous positive airway pressure device (CPAP), a mask that rests over your nose and mouth helps that helps keep your airways open while you snooze.

2. Fruity breath is a symptom of diabetes

Credit a complication of diabetes called diabetic ketoacidosis (DKA), which occurs when your body runs low on insulin and your blood sugar spikes, says Robert Gabbay, M.D., Ph.D., chief medical officer at the Joslin Diabetes Center in Boston. People with type 1 diabetes generally experience it more than those with type 2 diabetes do.

Here’s what’s happening: Your body can’t create the energy it needs to function properly, so it begins to break down fatty acids for fuel. This creates a build-up of acidic chemicals called ketones in your blood. One of the main acids—acetone (the same component found in nail polish remover)—can leave a fruity smell on your breath, Dr. Gabbay says. You might not notice it until someone else mentions it, but doctors can smell it on you as soon as you walk into a room.

The effects of DKA can be serious—even deadly. It can make you vomit and urinate frequently, causing your body to lose fluids at a dangerous rate, he says.

DKA generally occurs with other symptoms of diabetes, like fatigue, blurred vision, and unexplained weight loss, but in many cases, people don’t put them all together, which delays diagnosis and treatment. So if you notice the fruity odour on your breath along with any of those symptoms—especially if they are accompanied by fatigue, dry mouth, difficulty breathing, or abdominal pain, head to the emergency room as soon as possible, the American Diabetes Association recommends.

After your doctor tests your blood for ketones, he or she will work on replacing lost fluids and getting your sugar levels back to normal with insulin treatment.

3. Stinky feet is a symptom of athlete’s foot

Can’t seem to fight funky sneakers? A fungal infection may be to blame. If you notice dry, scaly skin around your toes, redness, and blisters, you may have athlete’s foot, according to the American Podiatric Medical Association (APMA).

Your feet might also emit a foul odour, caused by a combination of bacteria and fungus eroding into your skin and toe webs, says Cameron Rokhsar, M.D., associate clinical professor of dermatology at the Mount Sinai Hospital in New York. And if you scratch your feet and then touch another part of your body, you can spread athlete’s foot to other areas of your body, like your groin or armpit. That can potentially cause an odour to form in those areas, too.

Plus, if you ignore athlete’s foot, the skin in between your toe webs becomes excessively soft and moist, making it an entry point for bacteria, says Dr. Rokhsar. You can develop more complicated conditions like cellulitis, a bacterial infection of your skin’s soft tissue.

So if you’re experiencing symptoms, try an over-the-counter antifungal spray. If the problem continues to persist after two weeks, your doctor can take a closer look and prescribe a more targeted treatment, suggests the APMA.

Since athlete’s foot is just one of the nasty skin conditions you can pick up at the gym, protect yourself from picking it up again by wearing shoes in the locker room. Because fungi tend to thrive in moist environments, try using a talcum to keep your feet dry if they tend to get sweaty.

4. Smelly poop is a symptom of lactose intolerance

When your small intestine doesn’t produce enough of an enzyme called lactase, it can’t digest lactose, a sugar found in dairy products, says Ryan Unargo, M.D., assistant professor of gastroenterology at Mount Sinai Hospital in New York.

So your small intestine directs lactose directly to your colon—instead of your bloodstream—where your gut bacteria ferment it. This can cause loose, foul-smelling stool, bloating, and smelly gas, Dr. Unargo says.

Lactose intolerance is fairly common: In fact, an estimated 65 percent of people have trouble digesting dairy, according to the National Institutes of Health. But the reaction—including painful stomach cramping, nausea, diarrhoea, and vomiting, as well as smelly farts and poop— can vary from person to person, says Men’s Health nutrition advisor Alan Aragon, M.S.

For most people, though, it only takes 12 grams of lactose—about 220 millilitres of milk or a cup of ice cream—to set off unsettling symptoms, he says.

So if your gas or poop smells particularly pungent after you down some milk, you might want to check in with your doctor, says Dr. Unargo.

He or she can diagnose the problem, or even rule out more concerning intestinal issues, like Crohn’s disease, as a culprit behind the stench. Then, your doctor can help you determine how much lactose you can take in per day without causing a problem. (You can also pop a Lactaid pill, which contains the lactase enzyme and allows you to digest dairy within 45 minutes, if you just must have a sundae, Aragon says.)

5. Strong-smelling urine is a symptom of a urinary tract infection

Urinary tract infections (UTIs) can produce pungent, almost chemical-smelling urine, says Jamin Brahmbhatt, M.D., a urologist at Orlando Health. This happens after bacteria, most commonly E. coli, enter your urinary tract and urethra. Then, they multiply in your bladder, causing an infection.

UTIs are more frequent in women than men because their urethra—the channel that drains the bladder—is shorter. So men often ignore their smelly pee, since they figure they’re not at risk of one.

Not so: “Usually, men get infections if there’s something not allowing their bladder to drain” Dr. Brahmbhatt explains.

This means your UTI could be signalling a bigger problem, like kidney stones, diabetes, or an enlarged prostate gland, which can require surgery to treat, he says. So if you notice your pee smells funky, check in with your doctor, who will test your urine to see what’s up.

Bottom Line: If you feel like you are experiencing any of these symptoms, don’t try to self medicate, always consult a doctor.