The American Society of Clinical Hypnosis lists these as the three top myths about medical hypnosis:
People often fear that being hypnotized will make them lose control, surrender their will, and result in their being dominated, but a hypnotic state is not the same thing as gullibility or weakness. Many people base their assumptions about hypnosis on stage acts but fail to take into account that stage hypnotists screen their volunteers to select those who are cooperative, with possible exhibitionist tendencies, as well as responsive to hypnosis. Stage acts help create a myth about hypnosis which discourages people from seeking legitimate hypnotherapy.
Another myth about hypnosis is that people lose consciousness and have amnesia. A very small percentage of subjects, who go into very deep levels of trance will fit this stereotype and have spontaneous amnesia. The majority of people remember everything that occurs in hypnosis. This is beneficial, because most of what we want to accomplish in hypnosis may be done in a medium depth trance, where people tend to remember everything.
In hypnosis, the patient is not under the control of the hypnotist. Hypnosis is not something imposed on people, but something they do for themselves. A hypnotherapist simply serves as a facilitator to guide them.