Hot flashes: A sudden wave of mild or intense body heat caused by rushes of hormonal changes resulting from decreased levels of estrogen . Hot flashes can occur at any time and may last from a few seconds to a half-hour. They are due to blood vessel opening and constricting and a symptom of menopause .

Hot flashes are episodes that are experienced by many but not all women undergoing menopause. A hot flash is a feeling of warmth sometimes associated with flushing that spreads over the body and sometimes followed by perspiration. Menstruating women in their 40's may have hot flashes and hot flashes may last for a decade or more in some women. There is no way to predict when they will cease in a given woman. They decrease in frequency over time. The cause of hot flashes is not completely understood. Hot flashes may have more to do with fluctuation of hormone levels as opposed to low hormone levels per se.

Hot flashes can be treated with either oral (by mouth) or transdermal (patch) forms of estrogen. Both oral and transdermal estrogen therapies are available either as estrogen alone or as estrogen combined with progesterone . All available prescription estrogen replacement therapies whether oral or transdermal are effective in reducing hot flash frequency and severity. Generally available treatments decrease hot flash frequency by about 80-90%.