Heat Intolerance

Overview

Heat intolerance means your body finds it hard to cope with heat. You may feel uncomfortably hot, dizzy, sick, or worn out in warm places or during exercise. It is not a disease on its own. It is a sign that something is affecting how your body controls its temperature.

Yes, heat intolerance is common. Many people feel more sensitive to heat at some point, especially in hot weather, during menopause, or when they are unwell.

Anyone can be affected. It is more common in women around menopause, people with thyroid or hormone conditions, older adults, young children, people with long-term illnesses, and people taking some medicines.

Symptoms

Common symptoms

• Feeling very hot even when others are comfortable
• Sweating a lot, or sweating less than expected
• Flushing and red skin
• Headache
• Feeling sick or vomiting
• Dizziness or feeling faint
• Tiredness or weakness
• A fast heartbeat
• Muscle cramps
• Feeling irritable or easily upset

Symptoms in children

• Being more irritable or crying more than usual
• Feeling sleepy or floppy
• Poor feeding or refusing drinks
• Fewer wet nappies
• Hot, red skin
• Vomiting
• Confusion or unusual sleepiness — get urgent help

Symptoms in older adults

• Confusion or new forgetfulness
• Weakness or dizziness
• Fainting
• Feeling less thirsty than usual
• Sweating less than expected
• Hot skin
• A fast heartbeat

Causes

Main causes

• Hormone changes such as menopause or an overactive thyroid
• Some medicines, including water tablets and some medicines for heart, allergy, or mood problems
• Dehydration or not drinking enough
• Being in a hot place suddenly or working in heat
• Anxiety or panic
• Nerve or skin conditions that affect sweating
• Being overweight or having low fitness

Risk factors

• Being very young or older
• Having a long-term health condition
• Taking some medicines
• Living or working in a hot place
• Not being used to heat
• Drinking alcohol
• Using recreational drugs
• Being dehydrated

When to see a doctor

See a doctor urgently if:

• You feel confused, faint, or very weak
• You have a severe headache or keep vomiting
• Your heart is racing
• You stop sweating in hot conditions and feel very hot
• Symptoms do not improve after cooling down and resting

Book a routine appointment if:

• Heat intolerance is new or getting worse
• It affects daily life, work, or sleep
• You also have weight loss, a racing heart, or shaky hands
• You think a medicine may be causing it
• You have menopause symptoms
• You want advice on staying safe in hot weather

Diagnosis

Your doctor will talk with you about when symptoms happen, how long they last, your health history, and any medicines you take. They may ask about periods and menopause, heat exposure, and family history. A physical exam helps. They may arrange simple tests to look for causes.

Tests that may be done

• Blood tests to check thyroid, hormone, sugar, kidney, and salt levels
• A urine test
• A review of your medicines
• Sometimes a sweat test or a referral to a specialist

What to expect at your appointment

Most people need only a few simple tests. Your doctor will explain what they are checking and whether you need to see a specialist. Bring a list of all your medicines, including ones you buy without a prescription.

Treatment

Treatment depends on the cause. The main goal is to keep you cool and safe, treat any underlying condition, and review medicines that may be making heat harder to handle.

Self-care at home

• Move to a cool place, shade, or an air-conditioned room
• Drink water regularly; urine should be pale yellow
• Take cool showers or use cool damp cloths
• Wear loose, light-coloured clothes
• Use fans and open windows when it is safe
• Avoid alcohol and heavy meals in hot weather
• Rest and avoid hard exercise in the heat
• Plan outdoor activities for cooler parts of the day
• Check on yourself and others often

Medical treatments

Your doctor may review your medicines and suggest changes only if it is safe for you. They may treat a health problem that is making you heat intolerant, such as a thyroid or hormone condition. You may be referred to a specialist. Never stop or change a prescribed medicine without asking your doctor or pharmacist.

When is surgery considered?

Surgery is rarely used for heat intolerance itself. If another condition is causing it and needs surgery, your care team will explain that separately.

Living with this condition

Keep a cool drink with you, know the coolest rooms in your home, and have a plan for hot days. Tell family or friends if you feel unwell in heat. At work, ask about shade, breaks, and water.

Lifestyle tips

• Build activity slowly in cool conditions
• Keep your home cool by closing curtains in the day
• Use a thermometer to check room temperature
• Avoid hot tubs, saunas, and very hot showers if they trigger symptoms
• Wear a hat and sunscreen outdoors
• Carry a water bottle

Diet and exercise

Drink water before, during, and after exercise. Avoid alcohol and sugary drinks. Eat regular meals. Ask your doctor before adding extra salt, because some people need less salt, not more. Exercise in a cool gym or at cooler times of day. Stop if you feel dizzy, sick, or very hot.

Mental health and emotional wellbeing

Feeling unwell in heat can be worrying and can make you feel isolated. It is okay to ask for help. If you feel very distressed or hopeless, contact your local emergency number or a crisis support service in your country right away.

Prevention

Many heat problems can be prevented by staying cool, drinking enough, and getting advice about health conditions and medicines. Not every cause can be prevented, but you can lower your risk.

Vaccines

There is no vaccine for heat intolerance.

Screening programmes

There is no routine screening test for heat intolerance. If symptoms are new or worrying, your doctor can check for underlying conditions.

Complications

If left untreated

• Heat exhaustion, which can cause weakness, nausea, and fainting
• Heatstroke, a medical emergency
• Dehydration and kidney strain
• Falls or injuries from dizziness
• Worsening of heart or lung problems

Long-term outlook

Most people can stay safe and comfortable by keeping cool, drinking enough, and getting advice on any underlying cause. Heat illness is preventable, and getting help early makes a big difference.

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