A hot flash is an intense feeling of heat that comes on suddenly and isn’t caused by hot weather. When it happens, your face, neck, and chest turn red and warm, and you’ll break out in a sweat.

Hot flashes are most likely to happen when you’re in menopause, but other medical conditions can cause them, too. When hot flashes wake you up from sleep, they’re called night sweats. Here’s what you need to know.

Up to 80 percent of women in menopause get hot flashes. Yet every person experiences them a little differently.

In general, during a hot flash, a feeling of warmth suddenly floods your face and upper body. Your face and neck may turn red, like your skin is flushed or you’re blushing. Red blotches may also appear on your skin.

Other symptoms of a hot flash can include:

  • a fast or uneven heartbeat
  • heavy sweating
  • dizziness
  • shaking
  • a feeling like blood is rushing through your body
  • headaches

After the hot flash passes and the sweat evaporates from your body, you’ll feel chilled and may start to shiver.

A hot flash that hits at night — called a night sweat — can wake you up from a sound sleep.

Menopause is the main cause of hot flashes. During this transition, levels of the hormone estrogen fall. This drop in estrogen throws off your body’s “thermostat” — a gland called the hypothalamus at the base of your brain that regulates your internal temperature.

Lower estrogen levels send a signal to the hypothalamus that you’re too hot. In response, your brain sends a message to your body to cool you off — just as it would do if you were outside on a hot day:

  • Blood vessels near the surface of your skin widen (dilate) to release heat. This creates the red flush you see on your skin.
  • Your heart pumps faster.
  • Your sweat glands open up. The sweat evaporates off your skin to cool down your body.

All of these actions produce the rush of heat that you feel during a hot flash.

Your body temperature can also rise several degrees during a hot flash. This rush of heat can make you feel very uncomfortable.

Certain things you do can even set off or worsen hot flashes, including:

  • drinking strong coffee or tea
  • eating spicy foods
  • feeling stressed or anxious
  • being outside on a hot day
  • running a fever
  • dressing too warmly

Some people who have their ovaries surgically removed go into premature (‘surgical’) menopause. They can also develop hot flashes.

Other causes of hot flashes aren’t due to the same low estrogen levels that cause them during menopause. Chemotherapy or hormone treatment for cancer can also trigger hot flashes, as can alcohol and certain medications.

A few diseases have also been linked to hot flashes, including:

The average hot flash lasts from 30 seconds to 10 minutes. Everyone gets them with a different frequency and intensity.

In most people experiencing it during menopause, hot flashes last between 6 months and 2 years. Often this symptom will stop once you’ve completed the menopause transition.

Up to half of women report continued hot flashes for a few years after menopause. Some keep getting them for 10 years or more — well into their 70s or 80s. Things like your genes and hormone levels will dictate when this symptom stops.

Hot flashes can arrive intermittently or frequently. Some people get them several times an hour. Others get a few hot flashes a day. Still, others only have hot flashes once a week, or less often.

These events generally start occurring in perimenopause — the transitional time before menopause when your ovaries gradually produce less estrogen. You may note a spike as you move into menopause, which is defined as going one full year without getting a period. In most women, the frequency of hot flashes will decrease within a few years after menopause.

Avoiding triggers like spicy food and alcohol may help prevent at least some hot flashes. To ease your discomfort when a hot flash hits, dress in removable layers. Carry a fan and some wet wipes in your purse to cool you down when the heat gets too intense.

If the hot flashes are unbearable or interfere with your daily life, see a doctor. Hormone therapy, as well as some non-hormone medications, can help reduce the frequency of hot flashes.

If your hot flashes seem to be related to something other than menopause, you should also see a doctor to get checked out.