Achalasia is a digestive system disorder that makes it difficult to swallow food and drinks. In a healthy person, the muscles of the esophagus contract to push food down towards the stomach. This action, along with the relaxation of a ring of muscle at the end of the esophagus, allows food to pass into the stomach, enabling a healthy eating process. However, in individuals with achalasia, this process is impaired, making the passage of food and liquids difficult. Damage to the nerves in the esophagus, either due to an underlying cause or as a congenital anomaly, can lead to achalasia. The esophagus becomes progressively paralyzed and dilated. Ultimately, the esophagus loses its ability to propel food into the stomach. Food then accumulates in the esophagus, sometimes fermenting and regurgitating back into the mouth with a bitter taste.