Inducing vomiting isnt abnormal, even Dogs do it by eating types of grass..
However, when coupled with anxiety, stress and other factors (e.g weight), it can grow into Bulimia nervosa, not a condition i would say is abnormal, but rather an unhealthy one, and most commonly attributed to a mental disorder.
Im gonna shut up now, but will say that if youre sick, purging can sometimes be beneficial (eg detoxing), but routine purging can be detrimental, physically and mentally.
Just read the above post, i really dont mean to offend.