In the movie, Mrs. Doubtfire, Robin Williams dresses up as a woman and in one scene accidentally sets his dress on fire and calls that a "hot flash." We've all heard jokes like this before, but who really knows what hot flashes are and why some women experience them?

During a hot flash, the skin flushes bright red and breaks out in a heavy sweat. Other symptoms can include a pounding heart, a churning stomach, and a spinning head. This can last a few seconds or it might last several minutes.

Why do some women have hot flashes? Scientists haven't been able to come up with a definite answer yet, but they are sure that hot flashes are related the hormone estrogen. As women approach menopause, the production of estrogen fluctuates. This fluctuation of estrogen in the brain may affect nearby systems, including the temperature control center. Scientists speculate that the fluctuating estrogen can lead to some miscommunication between systems and turn on the temperature control center at inappropriate moments. Its the temperature control center that causes the symptoms of the hot flash.

Confused? Think back to gym class: you run around, you feel hot, you sweat, your skin flushes, then you cool off. This is temperature regulation in action. The difference between gym class and a hot flash is that when we exercise we really need to cool down. While in a hot flash, the brain is just confused by the fluctuating estrogen level. Once menopause is over, the brain becomes used to the new, lower level of estrogen, and the hot flashes cease.