What Causes Heat Intolerance?

Heat intolerance can be caused by reduced sweating, hormonal changes, medicines, dehydration, or difficulty releasing body heat. It describes an unusual difficulty coping with warm surroundings, rather than identifying one specific illness. The cause may be temporary, such as dehydration or a recent illness, or may need assessment when it is new, persistent, or worsening.

Your body normally cools itself through sweating and by sending more blood towards the skin. Heat intolerance can happen when sweating is reduced, fluid levels are low, or circulation and temperature control do not adapt well. Some medicines can affect sweating, blood flow, or the way your body responds to warmth, so a medication review may be useful.

Hyperthyroidism can present with increased sensitivity to heat, often alongside sweating, a fast or irregular heartbeat, shakiness, anxiety, or unexplained weight loss. Obesity can make heat loss more difficult because the body has a larger heat load to manage. These links do not diagnose the cause: similar symptoms can occur with dehydration, menopause, infection, anxiety, or other health conditions.

Move to a cool, shaded or air-conditioned place when symptoms begin. Loosen extra clothing, use a cool damp cloth on the neck or armpits, and drink fluids regularly unless a clinician has told you to restrict them. Avoid strenuous activity during the hottest part of the day, and take breaks in shade when exercising or working outdoors.

Keep a note of when the problem occurs, how long it lasts, your medicines and supplements, fluid intake, sweating, palpitations, and any weight or menstrual changes. Arrange a routine appointment if heat intolerance continues or interferes with normal activities. A clinician may check your medicines, hydration, thyroid function, and other possible causes. Do not stop a prescribed medicine without advice.

Seek urgent medical help if heat exposure is followed by confusion, fainting, a seizure, severe weakness, trouble breathing, chest pain, or inability to drink. Hot, dry skin or a very high body temperature is also concerning. Move the person to a cool place while help is arranged, but do not delay emergency care to try home cooling alone.

Heavy sweating, headache, nausea, dizziness, muscle cramps, and marked tiredness can be signs of heat exhaustion. If these symptoms do not improve promptly after cooling and drinking fluids, seek medical care because heat illness can worsen.

Ask whether any medicine or supplement could be affecting sweating or temperature control, whether thyroid testing is appropriate, and which symptoms should prompt urgent care. Tell the clinician if you have reduced sweating, palpitations, tremor, fever, recent illness, changes in weight, or symptoms that began after a new treatment.