Burps that smell distinctly of rotten eggs are caused by the release of hydrogen sulfide (H2S) gas. This foul odor is not spoiled food returning from the stomach, but a byproduct of microbial activity in the gastrointestinal tract. H2S gas signals that sulfur-containing substances are being broken down. Understanding whether the source is a temporary dietary reaction or an underlying medical issue is key to finding relief.
Understanding Hydrogen Sulfide Gas
The rotten egg smell is directly attributable to hydrogen sulfide (H2S). This gas is produced in the gut primarily by sulfate-reducing bacteria (SRB). These anaerobic microbes thrive in the digestive tract’s low-oxygen environment. SRB break down sulfur-containing compounds found in food, such as the amino acids cysteine and methionine, and inorganic sulfates.
During their metabolism, SRB generate H2S gas as a waste product. When this gas accumulates, it is expelled as a burp, carrying the pungent odor. While a small amount of H2S is normal, excessive production causes noticeable sulfur burps.
Common Dietary and Lifestyle Triggers
Sulfur burps are often a reaction to recently consumed foods rich in sulfur-containing compounds, which fuel sulfate-reducing bacteria. High-sulfur foods include:
- Cruciferous vegetables (broccoli, cauliflower, Brussels sprouts)
- Eggs
- Red meat
- Dairy products (milk and cheese)
- Alliums (garlic and onions)
Beverages like beer and wine also contain sulfates that gut bacteria can reduce, increasing H2S output. Lifestyle habits also contribute to gas accumulation. Eating meals too quickly or consuming large, heavy meals slows the digestive process. This slower movement gives bacteria more time to ferment food particles and generate gas. Swallowing excess air—such as when chewing gum, talking while eating, or drinking carbonated beverages—also increases the volume of gas expelled. Addressing these factors often resolves occasional sulfur burps.
Underlying Gastrointestinal Conditions
Persistent or frequent sulfur burps may indicate an underlying gastrointestinal issue. A primary chronic cause is Small Intestinal Bacterial Overgrowth (SIBO). In SIBO, an abnormally high number of sulfate-reducing bacteria colonize the small intestine, producing excessive H2S gas.
Infections with Helicobacter pylori (H. pylori) can also cause foul-smelling burps. This infection irritates the stomach lining and alters the balance of the upper digestive tract, favoring gas production. Parasitic infections like Giardia have also been linked to a gut imbalance that encourages hydrogen sulfide production.
Conditions causing slowed gastric emptying, such as gastroparesis, are another factor. When food remains in the stomach for an extended period, it ferments and feeds gas-producing bacteria. Certain medications, like GLP-1 receptor agonists used for weight management, intentionally delay stomach emptying, which can lead to H2S burps as a side effect.
Initial Steps for Relief and Medical Guidance
For immediate, occasional relief, temporary dietary adjustments, such as reducing high-sulfur foods, are effective. Staying well-hydrated supports digestion and helps the body process sulfur-containing proteins efficiently. Over-the-counter medications containing bismuth subsalicylate neutralize H2S gas directly.
If sulfur burps become frequent or are accompanied by other symptoms, medical evaluation is necessary. Warning signs include unintentional weight loss, severe abdominal pain, persistent vomiting, or blood in the stool. These symptoms suggest a potentially serious underlying condition that a gastroenterologist can diagnose and treat using specific testing, such as breath tests for SIBO or H. pylori.