Gas is caused by swallowing air and the breakdown of food in your digestive tract. The consequences are usually burping, feeling bloated, or passing gas. On average, most people pass gas at least 14 times per day. Some people have more gas than others, which may be uncomfortable or embarrassing.
The primary symptoms of IBS are abdominal pain or discomfort in association with frequent diarrhea or constipation and a change in bowel habits. There may also be urgency for bowel movements, a feeling of incomplete evacuation (tenesmus), bloating, or abdominal distension.
Setting aside the serious disease risks of smoking, for just plain old IBS the effects of tobacco can be immediate and downright violent. Tobacco irritates the lining of the intestines, which can cause diarrhea, intestinal cramping, pain, bloating, and gas. Nicotine can cause nausea and stomach cramps. Smoking also decreases the efficiency of food digestion and metabolism, which can cause altered bowel movements (already a problem for people with IBS) and bloating. Nicotine withdrawal can cause both constipation and diarrhea.