If it is serious enough, a medical evaluation is in order. There are two sources of intestinal gas. Some is swallowed. Carbonated drinks and foods like whipped cream and angel food cake contain excess gas. Many people actually swallow air when they are eating causing bloating.
Some people breathe incorrectly, swallowing air as they gasp or sigh.
Bacteria in your bowel generate the rest, forming several gases that smell bad. Certain foods like beans and cabbages promote gas formation. Fruits, milk, onions, asparagus and wheat produce gas in some people. A common parasitic infection of the bowel called Giardia can cause excessive gas. Lower end gas is called flatus .