1. The gas can build up in your digestive tract, causing discomfort and bloating. This can lead to abdominal pain. 2. Holding in a fart for an extended period can cause the gas to be reabsorbed into the bloodstream and eventually be expelled through your breath or other bodily functions. 3. The pressure from holding in a fart can sometimes force the gas back up into the intestines, causing reflux or heartburn.