Hypnosis (including feminization hypnosis) is absolutely safe, as shown by more than 200 years of hypnosis practice. In fact, you already experience hypnotic states in your daily life when you daydream or get engrossed in a book or movie – situations that commonly lead to a trancelike state.
You are always in total control of your own mind, and it is not possible for hypnosis to control or hurt you.
However, people with severe mental disorders such as psychosis or schizophrenia should only be hypnotized with consent from their mental health provider.