- Giardia, which is a parasitic infection that can be acquired from swallowing contaminated water and is known for its particularly pungent odour that’s hard to describe, Dr. Lee says. This is one of the most common intestinal parasitic infections in the U.S., according to the Centers for Disease Control and Prevention (CDC).
- Bacterial infections like Clostridium difficile, or C. diff, which can be contracted via hospital contamination and antibiotic usage, according to the Mayo Clinic. Dr. Lee says it can make poop smell sickly sweet.
- Viral infections like rotavirus, which can make poop smell foul, can be transmitted through contaminated food or if you touch a contaminated object and don’t wash your hands7.
5. Medications or supplements
Like food consumption, taking some daily medications or supplements can cause your poop to smell off, Dr. Lee says. Antibiotics, for example, strip your colon of good and bad bacteria and open up the possibility of infections like C. difficile, Dr. Pichetshote says. This can cause uniquely foul-smelling stool. Some supplements, like fish oil, can also result in a smellier-than-usual bowel movement, adds Dr. Lee. This is because certain nutrients can attach to undigested fat in your stool, causing it to stink8.
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, in which 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.
7. Inflammatory bowel disease
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.
8. Metabolic disorders
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.
9. Blood in the 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.
Should I worry about having a parasite in my poop?
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 diarrhoea 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 CDC.
How do I stop my poop from smelling?
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 diarrhoea-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: