Hot flashes are sudden episodes of mild to intense body heat brought on by hormonal fluctuations due to decreased levels of hormones. These episodes can occur at any time and may last from just a few seconds to up to half an hour. They result from the dilation and constriction of blood vessels and are a common symptom of menopause. Many women experience hot flashes during menopause, though not all do. These episodes often involve a sensation of warmth, sometimes accompanied by a flushed appearance that spreads across the body, and may be followed by sweating. Women in their 40s who are still menstruating may also encounter hot flashes, which can persist for a decade or longer for some. It is impossible to predict when they will stop for any individual woman, but they tend to become less frequent over time. The exact cause of hot flashes is not fully understood, but they seem more related to hormonal fluctuations rather than simply low hormone levels. To treat hot flashes, estrogen can be administered either orally or through a transdermal patch. These therapies are available as estrogen alone or combined with other hormones. All prescription estrogen replacement options, whether oral or transdermal, are effective in reducing both the frequency and severity of hot flashes, generally decreasing their occurrence by about 80-90%.