What should you know about extreme intolerance to heat?

Extreme intolerance to heat means your body struggles to stay comfortable or regulate temperature in warm conditions; persistent or severe symptoms deserve medical assessment. This may involve heavy sweating, a flushed feeling, unusual fatigue, headache, nausea, dizziness or a racing heartbeat. Heat intolerance is a symptom rather than a diagnosis, so the context matters: it can develop with an illness, medication, hormonal change or difficulty losing body heat.

Some people are more sensitive to heat because sweating or blood-flow changes do not cool the body effectively. An overactive thyroid can present with heat intolerance alongside sweating, tremor, anxiety, weight loss or a fast heartbeat. Higher body weight can also make heat loss more difficult. Medicines that affect sweating, fluid balance or alertness may contribute, including some medicines for allergies, mood, blood pressure or bladder symptoms. Fever, infection, menopause-related hot flushes and problems affecting the nervous system are other possibilities. A clinician may review your symptoms, medicines and medical history and check your temperature, pulse and thyroid-related signs.

Move to a cool, shaded or air-conditioned place and loosen extra clothing. Sip cool fluids if you are awake, able to swallow and not vomiting. Use a cool damp cloth, a fan or a lukewarm-to-cool shower; avoid putting ice directly on the skin. Pause exercise and avoid alcohol while symptoms settle. Record when the problem occurs, how long it lasts, your associated symptoms and any recent medicine or dose change. Arrange a routine appointment if the intolerance is new, keeps returning or interferes with sleep, work or activity. Do not stop a prescribed medicine without professional advice.

Seek emergency help if heat exposure is followed by confusion, fainting, a seizure, severe weakness, trouble breathing, chest pain or inability to drink. A very hot body, worsening symptoms or skin that becomes hot with little or no sweating can signal a heat emergency. Move the person to a cool place, remove excess clothing and cool the skin while emergency help is on the way; do not give fluids to someone who is confused, drowsy or unable to swallow. Prompt medical advice is also appropriate for repeated vomiting, severe headache or symptoms that do not improve after resting in a cool environment.

You could ask: Could a medicine or health condition be affecting my heat tolerance? Do my symptoms suggest a thyroid problem or heat exhaustion? Which checks or blood tests might clarify the cause? How should I manage exercise, work or travel in hot weather? What warning signs mean I should seek urgent help?