Heat Intolerance Symptoms & Top 4 Causes of Heat Intolerance

Heat intolerance is often associated with excessive sweating, blurred vision, irritability and frustration, or even nausea and cramps. Heat sensitivity is commonly caused by dehydration, a heat stroke, medication side effects, an overactive thyroid, menopause, or multiple sclerosis. Read below for more information on what can cause heat intolerance and treatment options.

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

  1. Heat Intolerance Symptoms
  2. Heat Intolerance Causes
  3. 5 Possible Heat Intolerance Conditions
  4. Heat Intolerance Treatments & Prevention
  5. Real-Life Stories
  6. Heat Intolerance FAQ
  7. Questions Your Doctor May Ask
  8. Statistics
  9. Related Articles
  10. References

What Does Heat Intolerance Mean? Your Symptoms Explained

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).

Common characteristics of heat intolerance

If you're experiencing heat intolerance, it can likely be described by the following:

  • Abnormal baseline temperature: 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
  • Other symptoms: You may experience muscle cramps, nausea, and vomiting with even a slight increase in temperature.

When is heat intolerance most likely?

The following conditions pose a greater risk for heat intolerance.

  • A neurological illness or condition: This means anything affecting your brain or other part of your nervous system.
  • A severe case of heat-related illness in the past
  • Anhidrosis: This means the sweat glands no longer function.
  • Multiple sclerosis
  • Dysautonomia: This 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

Are heat intolerance symptoms serious?

The severity of your heat intolerance is ultimately dependent on the cause.

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

What Can Cause Heat Intolerance?

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

Neurologic heat intolerance causes

Heat intolerance may be due to the following neurological causes.

  • Damage to the hypothalamus: This is the small part of your brain which controls body temperature through sweat to cool you off or shiver to warm you up.
  • Multiple sclerosis: People with MS 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: This means your sweat glands don't function and you are unable to sweat.

Other heat intolerance causes

Other various causes of heat intolerance include the following.

  • Dehydration
  • Previous cases of heat exhaustion or heat stroke: This may stress the body's cooling system until it no longer responds properly.
  • Recurrent fatigue: 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.
  • Medications and supplements: 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.

5 Possible Heat Intolerance Conditions

The list below shows results from the use of our quiz by Buoy users who experienced heat intolerance. This list does not constitute medical advice and may not accurately represent what you have.

Overactive thyroid

The thyroid is a small, bow-tie shaped gland in your neck. Its main job is to produce thyroid hormone (known as T3 or T4), which serves a wide array of functions throughout the body.

When too much thyroid hormone is released, the body’s metabolism gets ramped up, causing symptoms ...

Read more

Symptoms of menopause

Menopause is the name for the natural process by which the menstrual cycle (period) stops happening in a woman. Usually, the process is gradual (takes months or years) and occurs from the age of 45 to 55 years. Menopause is officially diagnosed once a woman stops having a period for 12 months continuously. A woman with menopause will notice a decrease in the number and regularity of her periods until they completely stop. In addition, she may notice a number of symptoms that occur as a result of decreased estrogen levels, such as hot flashes, changes in mood, sleep problems, vaginal dryness, changes in libido, and changes in sexual function. Certain medications exist that can decrease these symptoms.

Rarity: Common

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

Urgency: Self-treatment

Heat Intolerance Symptom Checker

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Postpartum thyroiditis

Postpartum thyroiditis means that an inflammation of the thyroid gland occurs just after childbirth. The thyroid, located in the neck, manufactures the hormone needed for proper metabolism. Thyroiditis causes it to first secrete too much thyroid hormone and then too little.

The cause is not known for certain. It may be an autoimmune condition similar to Hashimoto thyroiditis, where the body's own immune system interferes with normal functioning of the thyroid gland.

Most susceptible are women who also have type 1 diabetes or a family history of thyroid disease.

Symptoms may first include signs of an overactive thyroid, including nervousness, rapid heartbeat, and unintentional weight loss. Later signs are those of an underactive thyroid and include fatigue, sensitivity to cold, and weight gain.

Thyroid disorders can interfere with quality of life, but are easily treated by a medical provider.

Diagnosis is made through blood tests.

Treatment involves prescription medication for either the overactive or underactive thyroid, followed by regular monitoring and adjustment of medication.

Rarity: Uncommon

Top Symptoms: fatigue, irritability, anxiety, depressed mood, racing heart beat

Urgency: Primary care doctor

Multiple sclerosis (ms)

Multiple sclerosis, or MS, is a disease of the central nervous system. The body's immune system attacks nerve fibers and their myelin covering. This causes irreversible scarring called "sclerosis," which interferes with the transmission of signals between the brain and the body.

The cause is unknown. It may be connected to a genetic predisposition. The disease usually appears between ages 20 to 50 and is far more common in women than in men. Other risk factors include family history; viral infections such as Epstein-Barr; having other autoimmune diseases; and smoking.

Symptoms include numbness or weakness in arms, legs, or body; partial or total loss of vision in one or both eyes; tingling or shock-like sensation, especially in the neck; tremor; and loss of coordination.

Diagnosis is made through patient history, neurological examination, blood tests, MRI, and sometimes a spinal tap.

There is no cure for MS, but treatment with corticosteroids and plasma exchange (plasmapheresis) can slow the course of the disease and manage symptoms for better quality of life.

Rarity: Rare

Top Symptoms: severe fatigue, constipation, numbness, decreased sex drive, signs of optic neuritis

Urgency: Primary care doctor


Fibromyalgia is a set of chronic symptoms that include ongoing fatigue, diffuse tenderness to touch, musculoskeletal pain, and usually some degree of depression.

The cause is not known. When fibromyalgia appears, it is usually after a stressful physical or emotional event such as an automobile accident or a divorce. It may include a genetic component where the person experiences normal sensation as pain.

Almost 90% of fibromyalgia sufferers are women. Anyone with rheumatic disease, such as rheumatoid arthritis or lupus, may be more prone to fibromyalgia.

Poor sleep is often a symptom, along with foggy thinking, headaches, painful menstrual periods, and increased sensitivity to heat, cold, bright lights, and loud noises.

There is no standard test for fibromyalgia. The diagnosis is usually made when the above symptoms go on for three months or more with no apparent cause.

Fibromyalgia does not go away on its own but does not get worse, either.

Rarity: Common

Top Symptoms: fatigue, arthralgias or myalgias, anxiety, depressed mood, headache

Symptoms that always occur with fibromyalgia: arthralgias or myalgias

Urgency: Primary care doctor

Possible Treatments for Your Heat Sensitivity

When heat intolerance is an emergency

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: This 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.

When to see a doctor for heat intolerance

You should schedule an appointment for the following.

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

At-home treatments for heat intolerance

You can try the following remedies at home to address your heat intolerance symptoms.

  • Stay hydrated with plenty of cool water: Regardless of whether you are indoors or outdoors.
  • Wear loose, lightweight clothing in warm weather: Also be sure to wear 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
  • Try to keep a consistent temperature: 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: This can help to cool you off all over.
  • Look into specially made cooling garments: Such as a cooling vest

Real-life Stories

Once your story is reviewed and approved by our editors, it will live on Buoy as a helpful resource for anyone who may be dealing with something similar. If you want to learn more, try Buoy Assistant.

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 bodys ability to modulate temperature, particularly due to damage to the nervous system. A wide range of conditions, such as Parkinsons 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

To diagnose this condition, your doctor would likely ask the following questions:

  • Are you feeling irritable (easily made upset)?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Do you have trouble sleeping?
  • 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

Heat Intolerance Symptom Checker

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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 Buoy Assistant (a.k.a. the quiz).

Heat Intolerance Symptom Checker

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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, Sderhamn 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. WilsonsTemperatureSyndrome.com. WilsonsTemperatureSyndrome.com Link
  6. Viera AJ, Bond MM, Yates SW. Diagnosing Night Sweats. American Family Physician. 2003;67(5):1019-1024. AAFP Link

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