What Causes Hot Flashes?

Hot flashes (also called hot flushes) can be caused by a drop in estrogen, which happens with natural menopause. Some breast cancer treatments also lower estrogen levels — this can cause what’s called medical menopause.

Menopause — whether natural or medical — is the most common cause of hot flashes. During menopause, estrogen levels drop, which directly affects a part of the brain called the hypothalamus. You can think of the hypothalamus as your body’s thermostat; it helps control body temperature, as well as appetite, sleep cycles, and sex hormones. The drop in estrogen — along with other hormonal effects that come with menopause that aren’t well understood — confuses the hypothalamus and makes it think your body is too hot. Research suggests changes in serotonin after menopause may also lead to changes in the hypothalamus. Serotonin is a chemical called a neurotransmitter that helps your brain communicate with nerves throughout your body.

The brain responds to the hypothalamus by sending out an alert to the heart, blood vessels, and nervous system, telling them to cool down. As your heart pumps faster, the blood vessels in your skin dilate to circulate more blood to get rid of the heat, and your sweat glands release sweat to cool you off even more.

This is the same system that keeps your body from overheating in the summer. But when the process is caused by a drop in estrogen instead of actual heat, your brain's confused response can make you uncomfortable. It doesn’t help that hot flashes happen at unpredictable and often inconvenient times. Your body is working to cool itself down when it doesn’t need to, and you may find yourself soaking wet in the middle of the workday or waking up drenched in the middle of the night.

Research suggests that the quicker your estrogen levels drop, the more severe your hot flashes may be. 

Breast cancer treatments that can cause hot flashes include:

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  chemotherapy

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  hormonal therapy

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  ovarian suppression

All these treatments can lower estrogen levels, putting you in menopause. Hormonal therapies that lower estrogen levels or block the hormone’s effects commonly cause hot flashes. Tamoxifen can cause hot flashes in more than 50% of those who take it, including people who are post-menopausal and have already experienced hot flashes. Studies show that while aromatase inhibitors cause fewer hot flashes than tamoxifen, more than 30% of people taking an aromastase inhibitor have hot flashes.

The hot flashes usually increase over the first several months of treatment and then get better. If they don’t or they’re affecting your quality of life, talk to your doctor, who may be able to lower your dose or switch you to a different drug.

Other prescription medicines also can cause hot flashes, including opioids, antidepressants, certain medicines for osteoporosis, and some steroids.

If you’re already having hot flashes from menopause or breast cancer treatment, certain things, like stress, can trigger them. It can help to try to pinpoint your specific triggers so you can avoid them. You may want to keep a record of when a hot flash happens and note what you were eating or drinking, where you were, how you were feeling, and what you were wearing. 

Stress and anxiety

Stress and anxiety can boost the fight-or-flight response, which increases circulation and blood flow to the skin and can trigger a hot flash. Many people report stress as being their No. 1 hot flash trigger. There are many ways to manage stress, including exercise, tai chi, meditation, yoga, and breathing techniques. These tools are more helpful when you do them regularly, so find something you enjoy that you can incorporate into your routine. 

Alcohol

Alcohol contains chemicals that can cause your blood vessels to dilate, which can trigger a sensation of sudden heat and skin flushing. Alcohol is also linked to higher breast cancer risk. If hot flashes bother you while drinking, you may want to consider avoiding alcohol.

Smoking

It’s not news to anyone that smoking is linked to serious health problems, including cancer, stroke, and heart disease, but it may also trigger hot flashes. Nicotine can disrupt your hormonal balance by preventing the hormone androstenedione from converting to estrogen. This raises circulating testosterone levels. The result is a dip in estrogen levels, which can trigger a hot flash.

Diets high in fat and sugar

A 2020 paper that analyzed results from 19 studies found that eating more highly processed foods, saturated fats, and sugar was linked to more intense hot flashes.

Caffeine

Caffeine is a well-documented hot flash trigger. Drinking beverages high in caffeine, such as coffee or soda, may increase your heart rate and cause your blood vessels to dilate, triggering a hot flash. If you think your caffeine intake may be triggering hot flashes, consider switching to a beverage with little or no caffeine, like water, decaf coffee, or herbal tea.

Hot and spicy food and drinks

Hot food and drinks have both been linked to hot flashes. Sticking to room temperature or cool food and drinks can help, especially if you’re already feeling overheated. Avoid spicy foods and drinks, as well, as these also can trigger hot flashes. 

Hot weather

Hot weather and warm indoor environments can make hot flashes worse. Depending on your resources and where you live, there may not be a lot you can do about it. If you can turn on a fan or an air conditioner, do — or try opening a window. You can also go to public places with air conditioning, such as your local library or the grocery store to get relief.

Hot tubs, showers, and saunas

Just as you should avoid hot food, beverages, and weather if you’re having hot flashes, it’s best to avoid hot tubs, heated pools, hot showers and baths, and saunas. These can all trigger or worsen a hot flash. Stick to cool showers and baths to find some relief.

Becoming overheated

Becoming too warm during exercise or while wearing heavy or tight clothing can trigger a hot flash. To stay cooler while you’re working out, stay hydrated. Drink plenty of fluids before, during, and after you exercise. It’s best to avoid beverages with sugar and caffeine because they can dehydrate you. Wearing loose clothing, in layers, rather than wearing one big heavy sweater or coat, can help you avoid overheating during the day. Just take off and put on layers as you need to be comfortable.

Infections

A viral infection, like the flu or COVID, or a bacterial infection, like bronchitis or a urinary tract infection (UTI), can trigger a hot flash. This is because infections often cause a fever as your immune system raises your body temperature to help fight the illness. Infection-fighting medicines usually relieve a fever.

There are a number of ways to ease hot flashes, including medicine (both hormonal and non-hormonal), and natural remedies, such as yoga and acupuncture.