The smell of poop isn't exactly the most pleasant scent. It's not supposed to smell good. But if the stench of your stool suddenly becomes so out-of-this-world, you may wonder, "Why does my poop smell so bad?" First, don't panic. A stench that overpowers what's already considered pungent must signal something is wrong, right? Not exactly.
"The way poop smells can indicate a wide variety of things," Christine Lee, MD, a gastroenterologist at Cleveland Clinic, tells SELF. Most of the time, a foul scent alone isn't indicative of anything worrisome. But if there is an acute change in the smell of your number two that coincides with one or more symptoms like diarrhea, fever, chills, or unexplained weight loss, it could signal something more serious, Dr. Lee says.
Below is everything you need to know about what can change the smell of your poop, and when a wince-worthy sniff may signal something is off.
What causes foul-smelling poop? | How do I stop my poop from smelling? | How do I know if I have a parasite in my poop? | When should I go to the doctor?
Becoming acquainted with the scent of your poop sounds less than appealing, but establishing what's abnormal from your baseline can help determine when your bowel movements are especially rancid, Dr. Lee says. Here are some of the main causes of particularly bad-smelling poop:
"The first thing you might want to do is think back to what you ate," Dr. Lee says. "Whether it was eggs, Brussels sprouts, or tuna fish, those kinds of things can change the smell of the stool." Foods high in sulfur (think: meats, eggs, dairy, garlic, and cruciferous veggies like broccoli)1 are more difficult to digest, according to the Cleveland Clinic. When these foods move undigested into the large intestine, sulfur-metabolizing bacteria try to break it all down. This process creates odorless hydrogen and carbon dioxide gas (and sometimes methane) as well as odorous hydrogen sulfide-which mix into your poop and add an extra stench.
Like food consumption, taking some daily medications, supplements, and vitamins can cause your poop to smell particularly off, Dr. Lee says. Antibiotics, for example, strip your colon of good and bad bacteria and open up the possibility of infections like C. diff, Nipaporn Pichetshote, MD, a board-certified gastroenterologist at UCLA Health, tells SELF. This can cause uniquely foul-smelling stool. Some supplements and vitamins, like fish oil, can also result in a smellier-than-usual bowel movement, adds Dr. Lee. This is because vitamins can attach to undigested fat in your stool, causing it to stink2.
The next thing you want to consider is whether you might have a viral, bacterial, or parasitic infection. While a telltale sign is the accompaniment of other symptoms such as diarrhea, chills, fever, or unexpected weight loss, each infection can be identified by the unique scent of its chemical makeup of gasses. A few examples include:
"Being dehydrated increases your propensity to be constipated," Dr. Lee says. Feces consists of about 75 percent water and 25 percent organic matter (we're talking undigested carbohydrate, fiber, protein, and fat)4. When you're properly hydrated, that fluid helps your poop move more easily through the digestive tract and facilitates a healthy bowel movement. When you're in a state of dehydration, the fluids that usually help digested food pass through the intestines are absorbed by your stool instead5. "Constipated stool tends to have a different smell because it's been in your colon for so long," Dr. Lee says.
By now, you may have realized that the characteristics of your poop are largely dependent on what you consume. That said, some foods better aid in digestion than others. "Fiber can work in two ways: as a bulking agent in patients who have looser stools and as an osmotic laxative in those who are constipated," Dr. Pichetshote says. If you lack the necessary fiber to aid in bowel regulation, there's a chance you could become constipated or experience stool that's looser than usual.
With the former, which causes your stool to sit in your colon for longer, stool can begin to further ferment or break down6 and continue to yield gas such as hydrogen, methane, and carbon dioxide that lead to greater flatulence and more foul-smelling poop7.
The job of your small intestine is to absorb food's nutrients (vitamins, minerals, carbs, fats, and proteins) as it makes its way through your digestive tract. In certain medical conditions like Crohn's disease, where the small intestine lining is inflamed and sometimes damaged, nutrients may not be easily digested. Similarly, if you can't easily absorb lactose, a sugar found in milk products, then it can remain undigested and end up in the stool, where it ferments and gets stinky, Dr. Pichetshote says.
Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis, which are disorders that involve chronic inflammation of the digestive tract. When the digestive tract lining is inflamed (like in Crohn's disease) and the large intestine and rectum inflame and line with sores (like in ulcerative colitis), diarrhea, rectal bleeding, abdominal pain, fatigue, and weight loss can occur, per the Mayo Clinic. These symptoms can make it difficult to eat or for your intestines to properly absorb nutrients, leading to excess fat in the stool. Poop that contains excess fat produces more gas, which makes it especially foul-smelling.
Your metabolism serves to convert food into energy and remove toxins from the body. A metabolic disorder is when the process of either becomes disrupted and leads to a series of chain reactions. For example, in cystic fibrosis, the disruption comes in the form of thick mucus that blocks the digestive enzymes in the pancreas from reaching the small intestine, according to the Mayo Clinic. Chronic pancreatitis is another metabolic disorder that decreases the number of digestive enzymes produced, which are key in the breakdown of sugars, fats, and starches, according to Johns Hopkins Medicine. The result is malabsorption and foul-smelling stool.
Poop that smells like metal is usually a result of blood in the stool, according to Dr. Pichetshote, who adds that the scent is often accompanied by black stool or apparent blood. If your stool is black, you're likely having issues in your upper digestive tract, she says. If it's bright red, the problem is probably in the lower portion, particularly the colon or rectum.
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The key to less foul-smelling poop is to have a quality bowel movement, Dr. Lee says. That means one that's not too hard that it resembles constipation or too soft that it's diarrhea-like. You also want to feel like you've completely emptied your rectum. "The less you keep inside, the better and healthier you are," she says. To ensure a quality bowel movement, here are some things she recommends:
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Although certain symptoms might be able to indicate that you have a parasitic infection, the sniff test isn't going to be able to give you an answer one way or another. Whether you actually have a parasitic infection can only be confirmed through stool testing, according to Dr. Lee. She typically looks for fever and acute onset diarrhea before sending a sample for parasitic testing. Other symptoms of a parasite include gas, upset stomach or nausea, dehydration, and greasy poop that can float, according to the Centers for Disease Control and Prevention.
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Most of the time, a drastic change in stool scent is caused by something you ate, Dr. Lee says. So, if you notice your stool smells more pungent only when you eat certain foods-and you have no other symptoms-she suggests monitoring your stool to make sure it returns to baseline. If you haven't made any changes to your diet but notice a sharp change in the baseline of your stool that is persistent, doesn't improve, or is worsening, that's a change in bowel habits that might signal something is off, she says.
That's especially true when accompanied by other symptoms such as weight loss, new-onset diarrhea, fever, or chills. So while foul-smelling poop itself is not a reason to get worked up, persistently bad smells coupled with other symptoms warrant a call to your doctor. Together, you can figure out what's going on and how to get your poops back to their regular stinky selves.
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