What causes heat intolerance? 9 possible conditions

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Heat Intolerance

Most people do not like extreme heat, but if you have heat intolerance, you might find that it is impossible for you to be comfortable in hot weather. Heat intolerance may also be referred to as sensitivity to heat.

When you suffer from heat intolerance, it is often because your body is not regulating body temperature properly. Your body regulates its temperature by maintaining a delicate balance between hot and cold. The hypothalamus is a section of the brain that regulates your body’s temperature. When you get too hot, your hypothalamus sends a signal through your nerves to your skin, telling it to increase sweat production. When sweat evaporates off of your skin, it cools your body down.

What Leads to Heat Intolerance?

There are a number of potential causes for heat intolerance.


One of the most common causes of sensitivity to heat is medication. Allergy, blood pressure, and decongestant medications are among the most common. Allergy medications can inhibit your body’s ability to cool itself by preventing sweating. Blood pressure medicines and decongestants may cause a decrease in the blood flow to your skin, also inhibiting sweat production. Decongestants can also cause increased muscle activity, which can raise your body’s temperature.


Caffeine is a stimulant that can cause an increased heart rate and body metabolism. This can cause your body temperature to rise, leading to heat intolerance.


Hyperthyroidism is a condition that occurs when your thyroid gland produces too much of the hormone thyroxine. Thyroxine is important because it affects the regulation of your body’s temperature. Too much of this hormone can cause your body’s metabolism to increase, which leads to a rising body temperature. Hyperthyroidism is most commonly caused by Graves’ disease, an autoimmune disorder that occurs when your immune system makes antibodies against the thyroid gland, stimulating it to overproduce thyroid hormone.

Multiple Sclerosis (MS)

Multiple sclerosis (MS) is a debilitating disease that affects your central nervous system. The central nervous system is made up of your brain and spinal cord. The disease attacks the protective covering, or myelin, of the nerves of your central nervous system. Your myelin then becomes damaged, causing interruptions in your body’s nerve signals. This condition can possibly lead to heat intolerance.

What Are Some Signs I Should Look Out For?

Being heat intolerant can make you feel as though you are overheating. Heavy sweating is also extremely common in those that suffer from heat intolerance. The symptoms may occur gradually, but once the intolerance develops, it usually lasts for a day or two. Other potential signs of sensitivity to heat include:

  • headache
  • dizziness
  • weakness
  • cramping
  • nausea

Having a temperature between 100.4°F and 104.9°F when you are not otherwise ill can also signal that you are sensitive to heat. Your heartbeat might also be faster than normal.

Potential Complications of Heat Intolerance

If you have MS, heat intolerance can lead to you experiencing problems with your vision. This can range from blurred vision to temporary loss of vision. An increase in body temperature amplifies the distortion of your body’s nerve signals in those with MS. This is referred to as Uhthoff’s phenomenon, after Wilhelm Uhthoff who discovered the connection between heat and vision problems. This worsening of symptoms is only temporary and is usually resolved by cooling off.

Heat intolerance may lead to heat exhaustion under severe circumstances. If you experience signs of heat exhaustion or heat stroke, you may need to seek emergency medical treatment. These symptoms include:

  • confusion
  • loss of consciousness
  • vomiting
  • muscle cramps
  • body temperature of 104 F or higher
  • elevated heart rate
  • rapid breathing

If you experience these symptoms in conjunction with heat intolerance, seek medical attention immediately. Left untreated, heat exhaustion can lead to heat stroke, and heat stroke can be fatal.

Treating and Preventing Your Symptoms

There are a few things you can do to protect yourself from feeling the effects of heat sensitivity. Staying in a cooled environment is one of the best ways to avoid the negative symptoms. If you live somewhere that does not have air conditioning and you have MS, you may be able to deduct the cost of your fans and cooling equipment as a medical expense. This is usually only possible if your doctor has written you a prescription for it.

It is also recommended that you drink plenty of water to keep yourself hydrated. Profuse sweating can quickly dehydrate you. You might also try drinking refreshing iced drinks or snow cones. Wearing lightweight cotton fabrics will allow air to reach your skin and cool you. If you play sports, only wear extra protective gear like gloves, armbands, and hats when absolutely necessary.

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The thyroid gland produces a hormone that controls how your cells use energy (metabolize). Hyperthyroidism occurs when the body produces excessive amounts, causing rapid heart rates, weight loss, and heat intolerance.

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Graves' Disease

Graves disease is an autoimmune disorder that leads to hyperthyroidism and causes thyroid swelling.

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Multiple Sclerosis Overview

Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system. MS can cause varying symptoms that appear with a wide range of severity, from mild discomfort to complete disability.

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Peripheral Neuropathy

Peripheral neuropathy occurs when nerves malfunction because they're damaged or destroyed. You'll notice a tingling, numbness, or weakness, and possibly sweating, constipation, or diarrhea.

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This feature is for informational purposes only and should not be used to diagnose.
Please consult a healthcare professional if you have health concerns.
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