Hypnosis and Hypnotherapy are perfectly safe!
The answer is "no and possibly". There have been clandestine uses of hypnosis, e.g. some intelligence organisations have been known to engage in unethical uses. However, in a clinical and professional sense, it is entirely safe and can make some profound changes to people with many life-limiting conditions. Many of these conditions are based on dysfunctional responses to emotional and sensory misperceptions, even though the intent of these emotional responses are 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. In these instances, learning occurs both consciously and subconsciously and is then consolidated into a fear response during our ordinary nighttime sleep. Hypnotic learning, in terms of the solution, occurs at the subconscious level of memory and is therefore out of the reach of our conscious awareness. basically, this is because our conscious states often do more to exacerbate our issues, than they do to fix them! So, to a certain degree, we are sometimes using hypnosis to de-hypnotize the client?