According to a recent study, hypnosis can help cut hot flashes by as much as 74%.

The women who underwent hypnosis had five weekly sessions in which they received suggestions for mental images of coolness, a safe place, or relaxation, whatever their preference. They also got an audio recording of a hypnotic induction and were asked to practice it daily. The control group had five sessions in which a clinician provided discussion of their symptoms, attentive listening, interpersonal exchange, monitoring, measurement, and encouragement and avoided negative suggestions. The controls also got a recording that they were asked to listen to daily, but this one had information about hot flashes.
All the women kept diaries that tracked hot flash frequency and severity, and they also had hot flash frequency measured objectively by a skin conductance monitor. After 12 weeks, the women who underwent hypnosis reported 75% fewer hot flashes, compared with 13% fewer among the controls, and an 80% reduction in hot flash scores (a combination of frequency and severity), compared with 15% in controls. Skin conductance showed a 57% reduction in hot flashes for the women who underwent hypnosis, compared with 10% in the controls. The hypnosis participants also reported significantly less interference with their lives from hot flashes and better sleep than controls. Moreover, their level of satisfaction with the treatment was high.
How hypnosis eases hot flashes isn't clear. The authors of the study speculated that it may be because hypnosis may improve the function of the parasympathetic nervous system. This system is popularly called the "rest and digest" system, which puts the brakes on the sympathetic or "fight or flight" nervous system that controls body functions that ramp up during hot flashes, such as sweating and heart rate.
Source-Eurekalert