Many IBS sufferers turn to alternative or complementary medicine to try to help themselves, and some therapies can be very successful - hypnotherapy in particular has produced very good results in IBS patients. Unfortunately, there are also a number of alternative therapies which are dubious at best, and outright scams at worst.
A genuine therapist will be pleased to give you documentation and evidence about why their particular treatment works, as well as details of clinical trials to show its safety and efficacy. They will also be happy to prove their qualifications and membership of any professional bodies. If a therapist tells you that you should just trust them, and tries to make you feel guilty for even asking for some evidence, then that's the time to get up and leave.