The primary reason farts smell like rotten eggs is due to a gas called hydrogen sulfide, which is produced when bacteria in the large intestine break down certain foods containing sulfur. This sulfurous gas gives flatulence its characteristic unpleasant "rotten egg" odor.
Why Farts Smell Like Rotten Eggs
- The bacteria in the gut break down carbohydrates and other nutrients during digestion, releasing gases like hydrogen sulfide that contain sulfur, which smells like rotten eggs.
- Foods high in sulfur, such as eggs, meat, broccoli, cabbage, cauliflower, and Brussels sprouts, often cause this smell because they contain sulfur compounds that gut bacteria convert into hydrogen sulfide.
- Food intolerances, like lactose intolerance or fructose malabsorption, can also increase smelly gas production since undigested sugars ferment in the colon, releasing more sulfurous gases.
Additional Causes
- Constipation allows stool to stay longer in the colon, giving bacteria more time to produce smelly gases.
- Certain medications, infections, or digestive disorders such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD) may cause smelly flatulence as well.
In summary, farts smell like rotten eggs mostly because of sulfur-containing gases produced by gut bacteria digesting sulfur-rich foods. This is common and normal, although persistent or very foul smells could sometimes indicate an underlying digestive issue.
