The “rotten egg” smell of sulfur burps is hydrogen sulfide gas, which can come from something you ate, or a gut condition or infection. It’s helpful to understand where burps come from by first understanding where the gas originates. Beyond swallowing air, according to the National Institute of Diabetes and Digestive and Kidney Diseases, gas can enter your digestive tract when bacteria in your large intestine break down certain undigested foods. Foods with sulfur-containing compounds, like broccoli, brussels sprouts, and whole grains and milk products, can cause an uptick in sulfur-smelling burps and flatulence.
A condition called gastroesophageal reflux (GERD) causes bad-smelling gases in your stomach to come out of your mouth. Partially digested food in your stomach flows up the esophagus, creating discomfort and unpleasant burps. It can also cause heartburn or acid indigestion. If you think you may be experiencing GERD, contact your physician to discuss your symptoms and treatment.
Giardia is a waterborne infection that could also be responsible for your smelly burps. According to The Mayo Clinic, Giardia is an intestinal infection caused by a parasite that can enter your body through poor sanitation or contaminated water. While sulfur burps and diarrhea don’t go hand-in-hand, this is a case when it might. That’s because these microscopic parasites set up in your small intestine and become infections. They can cause diarrhea, poor appetite and weight loss, and foul-smelling burps. While it’s a temporary infection and should go away in a few weeks, it’s serious—and if you're suffering these symptoms, you should see your physician right away to get proper medications and treatment. There’s no vaccine to prevent giardia, but you can take measures to reduce your risk, especially when swimming in lakes, rivers, or swimming pools. Wash your hands, avoid swallowing water when swimming, and drink bottled water.