Vomiting is an unpleasant experience for most of us and there are people who have this abnormal and persistent fear of vomiting and this is called emetophobia. This fear might have been triggered by getting a stomach flu and having bouts of vomiting that was considered a traumatic experience for the person. One might have experienced vomiting in public and was embarrassed by it or was scolded for vomiting in public by a parent thus they associate vomiting with shame and something that can get them punished.
Some believe that this fear may be associated with fear of losing control. Most of the time, we cannot stop ourselves from vomiting if we feel nauseous. These people might also have frequent nausea and other problems of digestion such as vomiting or loose stools causing them to feel extremely anxious. Ironically, anxiety can also cause nausea and vomiting thus these people can have a cyclic problem.
On the other end of the spectrum, there are people who fear getting fat and these people induce vomiting. These people have bulimia and may suffer the effects of malnutrition. Later on, with psychotherapy, this need for vomiting that bulimics initially feel may be converted to fear of vomiting, especially with effective treatment.
Treatment usually includes controlling anxiety by psychotherapy or hypnotherapy. Most people may need anti-anxiety medications in the beginning but combined with psychotherapy, medications may be gradually withdrawn once symptoms are controlled.