Gas is one of the most common digestive problems that people experience. Excess gas may be felt as bloating, pressure and discomfort in the stomach and intestines. Excess gas is difficult for the body to expel because the gas bubbles get trapped in the stomach and intestines.

Several factors may cause excess gas to build up in the digestive tract:

Air swallowing
Certain foods and beverages
Poor muscle tone
Smoking
Chewing gum
Even wearing tight-fitting clothing

What causes gas?
There are 3 main causes of gas:

Swallowed air, called aerophagia. Although a normal amount of swallowed air is natural, excessive amounts often result in belching.
The movement of gas between the intestine and the bloodstream.
The production of gas due to digestive bacteria breaking down carbohydrates (complex sugars) in the small intestine. Beans, bran, broccoli, brussels sprouts, cauliflower and dairy products contain carbohydrates and may lead to the production of gas.

How anti-gas medicines work
Anti-gas medicines work to group individual gas bubbles into a larger bubble. This action speeds the passage of gas through the system either through belching, passing flatus (gas), or increasing the absorption of gas into the bloodstream.