Look, we all know that poop is 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?” 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, MDa gastroenterologist at Cleveland Clinic, tells SELF. Most of the time, a foul scent alone isn’t indicative of anything worrisome. But if there is a change in the smell of your number two that coincides with other potentially concerning 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?
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:
1. Sulfur-rich foods
“The first thing you might want to do is think back to what you ate,” he said. 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 stench2.
“Being dehydrated increases your propensity to be constipated.” Lee says. Feces consists of about 75% water and 25% organic matter (we’re talking undigested carbohydrate, fiber, protein, and fat)3. 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 dehydrationthe fluids that usually help digested food pass through the intestines are absorbed by your stool instead4. “Constipated stool tends to have a different smell because it’s been in your colon for so long,” he said. Lee says.
3. Lack of fiber
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,” Nipaporn Pichetshote, MDa board-certified gastroenterologist at UCLA Health, tells SELF. 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 down5 and continue to yield gas such as hydrogen, methane, and carbon dioxide that lead to excessive gas and more foul-smelling poop6.
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, certain infections can be identified by the unique scent of their chemical makeup of gasses. A few examples include: