Heat Intolerance: Causes and Symptoms

Very hot climates can produce discomfort in some people and this is known as 'heat intolerance'. Do you want to know more about it? Read on and we'll explain it to you.
Heat Intolerance: Causes and Symptoms
Leonardo Biolatto

Reviewed and approved by the doctor Leonardo Biolatto.

Last update: 25 October, 2022

The temperature of the environment can affect people differently. Because of this, many people greatly dislike hot weather. However, the problem lies when, beyond a dislike, this person is unable to withstand high temperatures, which may be known as heat intolerance.

To understand this phenomenon, it is important to know that the body automatically regulates its temperature. This is achieved through the hypothalamus, which activates various peripheral mechanisms to keep it within normal values. This organ is located at the base of the brain and is also involved in the sensation of thirst, hunger, and the production of breast milk.

Heat intolerance is a syndrome in which people feel very uncomfortable in high temperatures. This can lead to excessive sweating and a feeling of overheating.

What may be the causes of heat intolerance?

The specific reason why this syndrome occurs is still unknown. However, studies show that an error in the transcription of certain genes may be a predisposing factor. On the other hand, some specialists prefer to treat it as a psychological problem.

Generally speaking, all situations that affect central or peripheral temperature regulation can trigger heat intolerance. In addition, pathologies or substances that accelerate the metabolism of individuals are also causative agents.

A woman with heat intolerance.
Menopausal hot flashes are a frequent cause of heat intolerance among women over 40 years of age.

Medication use

Medication use is probably the most common cause of heat sensitivity. Drugs such as decongestants used to treat allergies and antihypertensives are responsible for cases of heat intolerance.

All these drugs prevent the production of sweat, which means the body can’t dissipate heat on its own. In addition, decongestants increase muscle activity, so the body will produce even more heat.


Caffeine is a stimulant substance that has the ability to increase the heart rate and accelerate the metabolism. In this way, the body will be producing more heat than in normal conditions, which can trigger the problem.


Hyperthyroidism is a pathology characterized by an overproduction of thyroid hormones, especially thyroxine. This hormone is involved in the growth and development of the individual by increasing energy production. In excess, it tends to accelerate the metabolism, which increases the body temperature.


When women reach a certain age they begin to suffer a hormonal imbalance that ends their reproductive stage; this is known as menopause. The hormonal changes suffered will generate a series of symptoms including sensitivity to heat, which can manifest itself as a sensation of hot flashes.

Multiple sclerosis

Multiple sclerosis is a serious disease that affects the central and peripheral nervous systems. It’s characterized by an autoimmune reaction in which the myelin sheath covering the nerves is destroyed. This means that nerve impulses can’t be transmitted properly.

Heat intolerance is a common complication in this disease, as the hypothalamus is unable to efficiently send the order to lower the temperature. However, the increase in body temperature in these patients is also related to physical, cognitive, and psychosocial fatigue.

When to see a doctor?

This health problem can take time to appear. However, once it manifests itself, it can last between 1 and 2 days. In most cases, sufferers are aware of the triggering factor. However, a doctor should always be consulted when there’s no apparent cause or when symptoms last more than two days.

On the other hand, people with multiple sclerosis should be very attentive to the symptoms. It’s important to visit the doctor if vision becomes blurred, as this could be due to Uhthoff’s phenomenon, a series of neurological changes, especially visual, caused by thermal failure.

Diagnosis of heat intolerance

The diagnosis of this condition is quite complex and often represents a challenge for the specialist. First of all, the clinical manifestations should be defined. Symptoms that may appear include the following:

  • An exaggerated sensation of heat with hyperhidrosis or excessive sweating
  • Headache and dizziness
  • Muscle weakness with cramps
  • Elevated body temperature

All of these symptoms usually appear in warm environments that are well-supported by other people. In addition, in order to try to find the possible cause, the doctor should analyze the patient’s medical history and perform various tests.

A man with heat intolerance.
The danger of heat intolerance when it causes hyperthermia conditions that affect normal cell metabolisms.

Discover more here: Prickly Heat: What Is It?

Treatment and prevention

In order to prevent all the symptoms of this syndrome, it’s important to stay in cool areas. The ideal thing is to have an air conditioner, although fans can also be useful.

In addition, it has also been shown that drinking a glass of cold water during exercise decreases the likelihood of an attack of heat intolerance.

On the other hand, if you’re already suffering from symptoms, it’s important for the person to stop their activities and for someone to remove them from the heat. The main objective will be to lower the person’s body temperature, and so the patient should drink plenty of water and move to a cool place.

Prevent heat intolerance to reduce bodily damage

It’s important to take all the necessary precautions in order to prevent this condition from developing, especially if you have already had previous episodes or if you have any predisposing factor. In this sense, you should wear loose and light clothing, and avoid physical activity at high temperatures.

On the other hand, it’s important to control heat intolerance once it occurs, as this can lead to a very dangerous condition called hyperthermia, or heat stroke. It is, therefore, a syndrome that shouldn’t be underestimated at any time and shouldn’t be taken lightly.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

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  • Hameau, S., et al. “Esclerosis múltiple y readaptación al esfuerzo.” EMC-Kinesiterapia-Medicina Física 41.4 (2020): 1-15.
  • Hosokawa Y, Stearns R, Casa D. Is Heat Intolerance State or Trait?. Sports Medicine. 2019;49(3):365-370.
  • Heat & Temperature Sensitivity [Internet]. National Multiple Sclerosis Society. Available from: https://www.nationalmssociety.org/Living-Well-With-MS/Diet-Exercise-Healthy-Behaviors/Heat-Temperature-Sensitivity.
  • Chaseling G. Physiological Considerations of Heat Intolerance in People with Multiple Sclerosis [PhD Doctorate]. University of Sydney; 2018.
  • Infante Amorós, Adalberto, and Silvia Elena Turcios Tristá. “Hipertiroidismo.” Revista Cubana de Endocrinología 23.3 (2012): 213-220.
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This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.