Medical Matters > Temperature Regulation

ME Essential Spring 2022


Recently I went to the seaside for the day. It was very hot and I felt it was too much for me, so I went down to the sea to cool off – just paddling in the water (which was surprisingly cold – in fact, downright chilly). It was fine initially but then I started to feel off-balance and then ill, and had to get back to the car quickly (and I had to sit down on the way several times) and then lie down on the back seat of the car. What might have caused such a reaction?


Temperature control disturbance (also called disturbed thermoregulation in medical language) is a very common symptom in ME/CFS and normally includes marked sensitivity to hot and/or cold weather/temperatures. This sensitivity to changes in temperature is probably related to (in part) a problem with the hypothalamus – a small gland in the brain that acts as a thermostat for a range of normal body functions, including helping to maintain a normal and stable body temperature – and the way in which the autonomic nervous system controls the size of blood vessels in response to changes in temperature. Consequently, people with ME/CFS need to take great care when out in the hot weather and they need to follow medical guidance if they get too hot.

From what you say it sounds as though you have not coped with a fairly rapid exposure to hot weather and possibly developed a mild form of heat stroke. Rapidly cooling down in the sea may have actually exacerbated the problem. So please take care on the beach in the future. Here are some tips for dealing with hot weather – day and night:

  1. Wear lightweight and loose fitting cotton clothes and a wide brimmed hat if you have to go outside.
  2. Drink plenty of fluids to stay hydrated – but avoid too many caffeine containing drinks.
  3. Eat small regular meals.
  4. Reduce activity levels and stay indoors between 10am and 6pm – unless you really need to go out.
  5. Be aware of warning signs of heat related illness/heat stroke – nausea, headache, confusion, muscle cramps, feeling faint.
  6. Close the curtains and windows during the day in any room you want to stay cool, especially those that face the sun.
  7. Buy a fan for use if it’s really hot.
  8. Take a cold ‘hot water bottle’ to bed at night.
  9. Have a bowl of cold water and a flannel by the bedside at night to cool down with.
  10. Be aware that some drugs (eg antidepressants, antihistamines) can also affect temperature control mechanisms.

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Medical Matters is for information purposes only. The answers provided by Dr Shepherd and the ME Association’s other expert advisers should not be construed as medical advice. We recommend that any information you deem relevant is discussed with your GP as soon as possible. It is important to obtain advice from a GP who is in charge of your clinical care, who knows you well, and who can consider other likely causes for symptoms. Seek personalised medical advice whenever a new symptom arises, or an existing symptom worsens. Don't assume that new or worsened symptoms are a result of having ME/CFS.

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