Hot flashes are considered a “vasomotor” symptom. This means they are the result of a change in your body's ability to regulate the opening and closing of blood vessels. About 75 percent of all women passing through the stages of menopause will experience hot flashes during some part of the transition. Though hot flashes are a common symptom of menopause, in many cases they are a minor inconvenience rather than an alarming problem. Hot flashes (sometimes called hot flushes) often begin with an increase in heart rate and a slight feeling of warmth, usually occurring in the face, neck, and shoulders.

A Range of Symptoms

Women describe hot flashes differently, depending upon how frequent or how dramatic their symptoms are. Mild or moderate hot flashes may last anywhere from one to fifteen minutes and cause feelings of mild warmth, accompanied by light perspiration and a slightly dry mouth. After the flash passes, the skin may feel slightly clammy. Mild hot flashes pass with little or no impact on general feelings of well-being.

Severe hot flashes can last from thirty seconds to thirty minutes and cause the skin temperature to rise dramatically. The face, neck, and throat can become flushed and red, and the body can break out in heavy perspiration. A woman experiencing a severe hot flash can have difficulty breathing, and the hot flash can trigger panic attacks and anxiety. Afterward, the woman may be left with a headache, some nausea, and a general feeling of anxiety and exhaustion.

If hot flashes are severe or long lasting, they can have a negative impact on your health and well-being. Hot flashes that occur at night — often known as night sweats — can interrupt sleep and lead to daytime fatigue, exhaustion, and decreased mental abilities. The fear of breaking into a clothes-drenching sweat at work or during social events can lead to anxiety and even depression. When hot flashes ruin your sleep or prevent you from performing well during the day, it's time to take action.

What's Happening When You Have a Hot Flash?

Hot flashes are connected to changes in your estrogen levels, though the specific cause and effect relationship is still under study. Recent studies seem to point to a narrower “thermoneutral zone” in some women, meaning that their range of comfortable temperature becomes narrower. It is a lowering of the “sweat threshold” and your body is prompted to sweat with even small rises in body temperature.

Declining levels of estrogen set the stage for hot flashes and the actual hot flashes are the result of this sudden resetting of the body's thermostat. If your brain senses that your body is even a bit too hot — for any reason, including increased blood flow to the brain, a high ambient temperature, or even the ingestion of hot, spicy foods — it sends out a signal that your body needs to cool off, now! In response, your pituitary gland sends out luteinizing hormone (LH), which causes the blood vessels near your skin's surface to dilate to release heat through your skin. This heat-releasing action makes your skin temperature (and your body temperature) rise, followed by an increase in perspiration. The perspiration helps to cool the skin, which can result in a clammy feeling. If you've perspired heavily, you may be left damp and even chilly. Your body temperature drops and your blood vessels constrict. If you are damp and cold, you may begin to shiver. That's the hot flash in action.

Common Hot Flash Triggers

Estrogen levels alone do not predict hot flashes and other factors can cause them or contribute to their severity. Many women find, for example, that they have hot flashes during periods of anxiety and nervousness; other studies have found that some prescription blood pressure medications and anti-anxiety medications may also cause hot flashes. Hot flashes may be your body's reaction to certain foods or beverages or even the temperature of the air around you — some women report their hot flashes are more severe and last longer when they occur during hot weather or in a hot room.

How Many, How Bad, How Long?

Although many women don't seem to notice hot flashes until after menopause has occurred, many others begin having them during peri-menopause, with forty-eight being an average age for the onset of hot flashes. In general, women who experience hot flashes start having them at least one year before menopause, and continue having them for one to six years.

The American College of Obstetricians and Gynecologists's publication Managing Menopause lists the findings of one study in which 501 women were asked about the frequency and severity of their hot flashes. Of those participating in the study, 87 percent reported having one or more flashes per day; of those experiencing multiple daily hot flashes, the numbers of incidents per day ranged from five to fifty, with one-third of the women reporting more than ten. Another study reported a lower frequency of hot flashes — participants had an average of only three or four flashes a day.