From the wikipedia page about emetophilia:
An online site theorizes, "vomiting was probably something either arousing or frightening to emetophiles at some point ... it aroused powerful emotions, and the emetophier called upon these emotions for the purpose of sexual gratification." (
Frequently Asked Questions about Vomiting)
Emetophilia may be related to
emetophobia, the fear of vomiting.
Many emetophiles, ironically, continue to fear vomiting themselves despite the amount of time they spend fantasizing about other people vomiting.
So please stop the judging guys.