Heat intolerance is a

symptom Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

characterized by feeling overheated in warm environments or when the surrounding environment's temperature rises. Typically, the person feels uncomfortably hot and sweats excessively. Compared to

heat illness Heat illness is a spectrum of disorders due to increased body temperature. It can be caused by either environmental conditions or by exertion. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the ...

es like heatstroke, heat intolerance is usually a symptom of endocrine disorders, drugs, or other medical conditions, rather than the result of too much exercise or hot, humid weather.

Symptoms

* Feeling subjectively hot * Sweating, which may be excessive In patients with

multiple sclerosis Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...

(MS), heat intolerance may cause a pseudoexacerbation, which is a temporary worsening of MS-related symptoms. A temporary worsening of symptoms can also happen in patients with

postural orthostatic tachycardia syndrome Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon sitting up or standing. POTS is a disorder of the autonomic nervous system that can lead to a variety of symptoms, ...

(POTS) and

dysautonomia Dysautonomia, autonomic failure, or autonomic dysfunction is a condition in which the autonomic nervous system (ANS) does not work properly. This condition may affect the functioning of the heart, bladder, intestines, sweat glands, pupils, and ...

Diagnosis

Diagnosis is largely made from the

patient history The medical history, case history, or anamnesis (from Greek: ἀνά, ''aná'', "open", and μνήσις, ''mnesis'', "memory") of a patient is a set of information the physicians collect over medical interviews. It involves the patient, and even ...

, followed by

blood test A blood test is a medical laboratory, laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a hypodermic needle, or via fingerprick. Multiple tests for specific blood components, such as a glucose ...

s and other

medical test A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic ...

s to determine the underlying cause. In women,

hot flash Hot flushes are a form of flushing, often caused by the changing hormone levels that are characteristic of menopause. They are typically experienced as a feeling of intense heat with sweating and rapid heartbeat, and may typically last from t ...

es must be excluded.

Causes

Excess

thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones triiodothyronine, T3 and T4 rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-releasing hormone rect 297 168 502 200 Hypothalamus r ...

, which is called ''

thyrotoxicosis Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

'' (such as in cases of

hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

), is the most common cause.Wilkins, Lippincott Williams &.
Nursing: Interpreting signs & symptoms
'. Lippincott Williams & Wilkins; 2007-03-01 . . p. 306–307. Other causes include: *

Amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...

s along with other types of stimulant medications, such as appetite suppressants *

Anticholinergics Anticholinergics (anticholinergic agents) are substances that block the action of the acetylcholine (ACh) neurotransmitter at synapses in the central and peripheral nervous system. These agents inhibit the parasympathetic nervous system by sel ...

and other drugs that can impair sweating *

Caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...

* Malignant hyperthermia susceptibility *

Menopause Menopause, also known as the climacteric, is the time when Menstruation, menstrual periods permanently stop, marking the end of the Human reproduction, reproductive stage for the female human. It typically occurs between the ages of 45 and 5 ...

Multiple sclerosis Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...

Fibromyalgia Fibromyalgia (FM) is a functional somatic syndrome with symptoms of widespread chronic pain, accompanied by fatigue, sleep disturbance including awakening unrefreshed, and Cognitive deficit, cognitive symptoms. Other symptoms can include he ...

Diabetes Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...

* Hypothalamic tumors * Methadone treatment *

Dysautonomia Dysautonomia, autonomic failure, or autonomic dysfunction is a condition in which the autonomic nervous system (ANS) does not work properly. This condition may affect the functioning of the heart, bladder, intestines, sweat glands, pupils, and ...

Autonomic neuropathy
from U.S. National Library of Medicine's ''MedLine Plus''. Accessed 2015-05-20. *

Postural orthostatic tachycardia syndrome Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon sitting up or standing. POTS is a disorder of the autonomic nervous system that can lead to a variety of symptoms, ...

(POTS) * Sensory defensiveness/sensory processing disorder *

Serotonin syndrome Serotonin syndrome (SS) is a group of symptoms that may occur with the use of certain Serotonin, serotonergic medications or Recreational drug use, drugs. The symptoms can range from mild to severe, and are potentially fatal. Symptoms in mild c ...

Treatment

Treatment is directed at making the affected person feel more comfortable, and, if possible, resolving the underlying cause of the heat intolerance. Symptoms can be reduced by staying in a cool environment. Drinking more fluids, especially if the person is sweating excessively, may help. Cooling vests can be used as a preventative tool to reduce a person's body temperature or when symptoms present to feel more comfortable.

References

{{Reflist Symptoms and signs Sensitivities