Hypnosis and Hypnotherapy are perfectly safe!
The answer is "NO". The reason is because hypnosis is a natural phenomena, it was discovered, not created. However, some life limiting conditions can be harmful, even though the intent is positive! E.g. a fear of needles, the subconscious intent of the phobia is to keep you from harm, the downside, though, may be harmful because the content of the syringe may save your life!
In some sense hypnosis occurs in the negative, i.e. in trance states we can develop unwanted behaviours, again citing the fear of needles, this may have developed as a response to observing someone else reacting to a painful injection. It could also be conscious, perhaps as a result of knowing someone contracting an awful disease through using an infected syringe, or even an ordinarily safe routine or procedure like a blood transfusion. Hypnotic learning occurs at the subconscious level and is therefore always out of the reach of conscious awareness. So, to a certain degree, we are sometimes using hypnosis to de-hypnotize the client?
So, hypnosis itself is not harmful or dangerous but occasional adverse effects of this natural process, as in the everyday experience of hypnotic phenomena, can create unwanted or unpleasant side effects. But please remember, I said, "as in the everyday experience of hypnotic phenomena". This is not the same thing as a hypno-therapeutic intervention or a consequence of hypnotherapy, but rather the natural consequence of normal living. In the clinical environment, the therapist is looking to make behavioural change at the subconscious level and that, is never considered dangerous.