Stage hypnotism is potentially dangerous even though it depends mostly on the exhibitionism of those taking part, according to experts on the medical uses of hypnotism.

Dr Hamilton Gibson, the president of the British Society of Experimental and Clinical Hypnosis, believes that ``some people love an excuse to be exhibitionists on stage and do daft things which they wouldn't normally do.'' But, he warned, there are aboutten to 15 per cent of the population who are genuinely susceptible.

The performance aspect was emphasised also by Dr Michael Heap, lecturer in clinical hypnotism at Sheffield University, ``In the end there may not be a real distinction between acting and reality for those who go into trances during stage hypnotism acts, '' he said Such people ''have a genuine experience of getting deeply involved in the hypnotist's suggestions.'' They get so profoundly caught up, he believes, that they suspend normality.

Georges Philips, a hypnoanalyst, also believes that ``no one can be hypnotised against their own will. Nobody would do anything that they would not consciously do.'' He believes hypnosis is a natural phenomenon, in between being asleep and awake.

The hypnotic trance is where someone gets immersed in something that is going on inside them, according to Dr Heap. It can be imagination, memory or fantasy, with the hypnotist orchestrating the experiences.

Hypnotism has two main applications in conventional medical practice. One is to make suggestions which will alter people's experiences: the way they think, feel and behave.

The second use is based on the assumption that people in a trance are more in touch with things below the level of common emotions. There are case studies showing that under hypnosis people can get access to emotions which have been partly suppressed. DrHeap cited the example of a trauma, recent or past, which is there but is too anxiety provoking to be accessible normally.

Dr Gibson stressed that practitioners should use hypnosis only as an adjunct to their normal professional expertise. ``There is no such thing as hypnotherapy. It's humbug. You can't hypnotise people's ills away.''

All three called for tighter regulation of stage hypnosis acts.