Read below about heat intolerance, including causes, treatment options and remedies. Or get a personalized analysis of your heat intolerance from our A.I. health assistant. At Buoy, we build tools that help you know what’s wrong right now and how to get the right care.

This symptom can also be referred to as:
Always feeling hot

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Heat Intolerance Symptoms

Heat intolerance, also called heat sensitivity, means that your body's usual methods of cooling itself are not working properly and you are unable to adjust normally to changes in the surrounding temperature [1].

Sweating, and dilating the blood vessels so that more heat can escape through the skin, usually work well together to keep heat from building up. With heat intolerance, however, you may feel very fatigued and ill with even a small increase in external temperature (such as experiencing a warm day or sitting in a hot tub) or internal temperature (having a fever or exercising).


  • Your baseline body temperature may be chronically too low or too high.
  • You may sweat heavily or not at all.
  • Your vision may become blurred.
  • You may experience muscle cramps, nausea, and vomiting with even a slight increase in temperature.

Most often affected by heat intolerance symptoms are those with:

  • A neurological illness or condition, which means anything affecting your brain or other part of your nervous system.
  • A severe case of heat-related illness in the past.
  • Anhidrosis, which means the sweat glands no longer function.
  • Multiple sclerosis.
  • Dysautonomia, which means the autonomic nervous system does not control the body's functions as smoothly as it should.
  • A low level of physical fitness.
  • High blood pressure.
  • Obesity.
  • Alcoholism or drug addiction.

Where in the world are heat intolerance symptoms most common?

  • Any place with a hot climate, of course.
  • The risk may be greater if the outdoor heat is accompanied by high humidity.

When are heat intolerance symptoms most likely to occur?

  • Heavy exercise may bring on the symptoms, even in cool air.
  • Sitting in a hot tub or a sauna always causes a rise in body temperature.

Are heat intolerance symptoms serious?

  • Heat intolerance must be monitored closely at all times so that it does not get out of control.
  • Heat exhaustion is the early stage of heat stroke.
  • Heat stroke, the uncontrolled rise in core body temperature, is a life-threatening medical emergency [2].

Heat Intolerance Causes Overview

Most cases of chronic heat intolerance are due to neurologic illnesses or from conditions you were born with.

Neurologic heat intolerance causes:

  • Damage to the hypothalamus, the small part of your brain which controls body temperature through sweat to cool you off or shiver to warm you up.
  • Multiple sclerosis patients often suffer from heat intolerance, because it is difficult for the damaged nerves to respond to the need for cooling, and 60 to 80 percent of people with MS find that heat exacerbates their symptoms [3,4].
  • Chronic anhidrosis, which means your sweat glands don't function and you are unable to sweat.

Other heat intolerance causes:

  • Dehydration.
  • Previous cases of heat exhaustion or heat stroke, which may stress the body's cooling system until it no longer responds properly.
  • An existing condition which causes ongoing fatigue. When you are very tired, your circulation slows and does not carry your blood to the skin's surface quickly enough to help you cool off.
  • A number of medications and supplements can interfere with your tolerance to heat, because they interfere with circulation and sweating. Blood pressure and allergy medications are high on this list, and so are diuretics because they can cause dehydration.

A.I. Health Assistant Causes for Heat Intolerance

The list below shows results from the use of our A.I. Health Assistant by Buoy users who experienced heat intolerance. This list does not constitute medical advice.

  1. 1.Overactive Thyroid

    The thyroid is a butterfly-shaped gland in the neck, just above your collarbone. It is one of your endocrine glands, which make hormones. Thyroid glands control how fast one burns calories and how fast the heart beats. If the thyroid is too active, it makes more thyroid hormones than the body needs. This is called hyperthyroidism.

    Great prognosis with high remission rates

    Top Symptoms:
    fatigue, anxiety, depressed mood, irritability, trouble sleeping
    Primary care doctor
  2. 2.Symptoms of Menopause

    Menopause is the point in life where your period stops. This happens when the ovaries stop making hormones that keep your cycle going. The transition into menopause is called peri-menopause and can include symptoms like hot flashes, shortening of menstrual cycle and mood fluctuations.

    Hot flashes typically peak approximately 1 year after the final period and last 4-10 years. Most women stop having hot flashes 4 years after they start, but 10% of women may have hot flashes up to 12 years after their last period.

    Top Symptoms:
    fatigue, delay in or irregular periods, vaginal discharge, anxiety, trouble sleeping
    Symptoms that always occur with symptoms of menopause:
    delay in or irregular periods

    Heat Intolerance Checker

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  3. 3.Postpartum Thyroiditis

    The thyroid is a butterfly-shaped gland in the neck, just above the collarbone, which produces hormones that control how fast calories are burned and how fast the heart beats. Postpartum thyroiditis is inflammation of the thyroid gland that occurs in women about 1 year after the delivery of a baby. This condition occurs in two phases. In the first phase, too much thyroid hormone is produced leading to rapid weight loss and a fast heartbeat. After 2-4 months, the second phase begins which may last up to a year, and is characterized by thyroid levels that are too low. Symptoms in the second phase include weight gain, fatigue, depression, and hair loss.

    Usually will resolve itself, but in some cases, lifelong hypothyroidism may develop requiring lifelong thyroid hormone replacement therapy.

    Top Symptoms:
    fatigue, irritability, anxiety, depressed mood, racing heart beat
    Primary care doctor
  4. 4.Multiple Sclerosis (Ms)

    Multiple sclerosis (MS) is a neurodegenerative disease in which the immune system attacks the myelin sheath. The myelin sheath is involved in carrying nerve signals so this damage causes interruptions in nerve signaling.

    This is a lifelong condition; however, treatment may be beneficial.

    Top Symptoms:
    severe fatigue, constipation, numbness, decreased sex drive, signs of optic neuritis
    Primary care doctor
  5. 5.Fibromyalgia

    Fibromyalgia is a disorder that causes widespread pain, tenderness, and fatigue.

    Fibromyalgia is generally a lifelong condition

    Top Symptoms:
    fatigue, arthralgias or myalgias, anxiety, depressed mood, headache
    Symptoms that always occur with fibromyalgia:
    arthralgias or myalgias
    Primary care doctor

Heat Intolerance Treatments and Relief

Seek immediate treatment in the emergency room or call 911 if:

  • You see signs of heat stroke. The person will have a high body temperature, rapid pulse, altered mental state or unconsciousness, and no sweating. While waiting for the ambulance, move the patient to a cool place and soak them with water.
  • You see signs of heat exhaustion, which is the early stage of heat stroke. The person is still sweating but has high body temperature, confusion, fatigue, headache, muscle cramps, nausea, and vomiting.

Schedule an appointment for:

  • Ongoing difficulty and discomfort from trying to cope with the heat.
  • Heat rash and otherwise irritated skin from constant overheating and sweating.

Heat intolerance remedies you can try at home:

  • Stay hydrated with plenty of cool water, whether you are indoors or outdoors.
  • Wear loose, lightweight clothing in warm weather, and natural fibers that "breathe" during cold weather.
  • Eat cold, fresh foods instead of heavier cooked foods.
  • Exercise outdoors only during the coolest part of the day, or only indoors in air conditioning.
  • Don't move from air-conditioned cold to the hot outdoors any more than necessary, as this causes stress on the body's cooling system.
  • Sitting with your bare feet in a basin of cold water can help to cool you off all over.
  • Look into specially made cooling garments, such as a cooling vest.

FAQs About Heat Intolerance

Here are some frequently asked questions about heat intolerance.

Can menopause cause heat intolerance?

During menopause, women commonly experience hot flashes, which are sudden, temporary onsets of body warmth, flushing, and sweating. Sometimes, hot flashes can also cause too much sweating, leading to night sweats — if occuring at night, of course. Nevertheless, heat intolerance has a number of other causes besides menopause.

Why is there heat intolerance in hyperthyroidism?

Elevated thyroid hormone in the body can increase not only basal metabolism but stimulate heat production, causing heat intolerance.

Can dehydration cause heat intolerance?

In severe cases of dehydration, an individual may experience heat intolerance due to an inability to sweat, which is the primary cooling mechanism of our body as sweat evaporates.

Why do I have a heat intolerance without sweating?

Women approaching and experiencing menopause can commonly experience heat intolerance without sweating (e.g. hot flash). In other circumstances, experiencing heat intolerance without sweating can indicate problems with the body’s ability to modulate temperature, particularly due to damage to the nervous system. A wide range of conditions, such as Parkinson’s disease and diabetic neuropathy, can cause such damage. In addition, certain medications can lead to autoregulation thermal dysfunction.

What's the difference between heat intolerance and excessive sweating?

Heat intolerance is a feeling of being overheated when the temperature around you rises. It can often cause heavy sweating. Excessive sweating (hyperhidrosis) is the secretion of sweat in amounts greater than physiologically needed for thermoregulation. It is most commonly a chronic condition with unclear etiologies, usually affecting the axillae, palms, and soles. Rarely, excessive sweating is a manifestation of systemic diseases (such as certain infections, nerve damage, malignancies) or due to certain medications [5,6].

Questions Your Doctor May Ask About Heat Intolerance

  • Q.Are you feeling irritable (easily made upset)?
  • Q.Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Q.Do you have trouble sleeping?
  • Q.Do you notice your heart beating hard, rapidly, or irregularly (also called palpitations)?

If you've answered yes to one or more of these questions, try our heat intolerance symptom checker to find out more.

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Heat Intolerance Symptom Checker Statistics

  • People who have experienced heat intolerance have also experienced:

    • 7% Fatigue
    • 6% Nausea
    • 5% Hot Flash
  • People who have experienced heat intolerance were most often matched with:

    • 42% Overactive Thyroid
    • 42% Postpartum Thyroiditis
    • 14% Symptoms of Menopause
  • Source: Aggregated and anonymized results from visits to the Buoy AI health assistant (check it out by clicking on “Take Quiz”).

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  1. Martin LJ. Heat Intolerance. U.S. National Library of Medicine: MedlinePlus. Updated February 18, 2018. MedlinePlus Link.
  2. Becker JA, Stewart LK. Heat-Related Illness. American Family Physician. 2011;83(11):1325-1330. AAFP Link.
  3. Flensner G, Ek AC, Söderhamn O, Landtblom AM. Sensitivity to Heat in MS Patients: A Factor Strongly Influencing Symptomology - An Explorative Survey. BMC Neurology. 2011;11:27. NCBI Link.
  4. Temperature Sensitivity. Multiple Sclerosis Trust. Updated May 2018. MS Trust Link.
  5. Heat and/or Cold Intolerance. Link.
  6. Viera AJ, Bond MM, Yates SW. Diagnosing Night Sweats. American Family Physician. 2003;67(5):1019-1024. AAFP Link.