You probably pass gas several times a day without even realizing it. That’s because most farts are odor-free and caused by swallowed air or healthy gut bacteria breaking down food, according to experts. But there are some farts that are just downright stinky. And while the frequency and odor of your flatulence may not always be a cause for concern, occasionally having particularly smelly gas can be a sign of something else going on in the digestive tract, says digestion expert Heather Moday.
One of the main reasons your farts might smell really bad is because you ate a lot of sulfur-heavy foods, such as eggs and meat. When the bacteria in your digestive system break down these foods, they create stinky compounds called sulfides that smell like rotten eggs. Other common culprits are complex starches, including those found in beans, raffinose (a type of sugar found in cruciferous vegetables like brussel sprouts and cabbage), and lentils. Food intolerances are also another common cause of smelly gas, particularly lactose intolerance. The body isn’t able to digest the milk sugar (lactose) that’s found in many dairy products, which leads to an accumulation of waste in the colon.
Consistently smelly farts can also be a sign of Irritable Bowel Syndrome (IBS), which is characterized by digestive issues like bloating and abdominal pain, and bacterial imbalances. If dietary changes don’t make a difference, book an appointment with your doctor. They’ll ask you about your symptoms and history to help narrow down a diagnosis.