Hello, Thanks for your query. While most burps do not have a pleasant odor, burps that smell like rotten eggs may be a sign of more serious digestion issues than a bad lunch. These smelly burps could be caused be a food allergy, and one of the most common is lactose, from milk. They could also be caused by more serious medical problems, such as acid reflux, gastroesophageal reflux disease (GERD), Crohn s disease, or irritable bowel syndrome. It would be best to consult with your primary care doctor and make note of any other digestive problems that you may notice. You should also consider keeping a food diary so that you can note if there are specific foods you eat that bring on the rotten egg burps more frequently. I do hope that you have found something helpful and I will be glad to answer any further query. Take care