Uhthoff’s Phenomenon Explained

Poll results: heat sensitivity (Barts MS Blog)

Studies have shown that heat sensitivity is a key clinical factor in MS.

Heat sensitivity in MS


60 to 80% of people with MS have excessive heat sensitivity issues.


  1. A slight increase in core body temperature (0.25°C to 0.5°C) rises the core body temperature because of nerve damage in MS patients.
  2. Nerve transmission requires more energy to work in the heat, and even more when there is demyelination.


  1. Physical exercise,
  2. Warmer environment,
  3. Cooking in front of a hot oven and over a hot stove,
  4. Eating or drinking hot food and/or fluids,
  5. Warm indoor and other heat-inducing surroundings.


  1. Temporary exacerbation of existing MS symptoms and new disturbing symptoms when exposed to elevated temperatures,
  2. ‘Pseudo-exacerbation’ of the symptoms as increase in temperature as such does not cause any nerve damage,
  3. Disturbance or block in the normal physiological nerve conduction mechanisms. Demyelination not only causes slowing of nerve impulse conduction along the affected nerve fibers but also linked to a phenomenon called Frequency Dependent Conduction Block,
  4. Premature fatigue,
  5. Energy down to a bare minimum,
  6. Recharging very hard to achieve,
  7. Intense limb weakness,
  8. Visual problems,
  9. Neuropathic pain due to damage caused to the thalamus and the spinothalamic-cortical pathways leading to thermo-regulatory dysfunction,
  10. Numbness,
  11. Pins and needles,
  12. Dizziness,
  13. Cognitive dysfunctions like memory problems,
  14. Judgment difficulties,
  15. Concentration difficulties,
  16. Language incomprehension,
  17. Slurred speech,
  18. Nauseous and a feeling of fainting about to happen.

How to handle?

  1. Avoid working outside during the warmest hours of the day (11am to 4pm),
  2. Seek out shade and/or carry an umbrella wherever you go,
  3. Take lukewarm showers,
  4. Keep your head and neck area cool with a wet, cool towel from the freezer,
  5. Stay well-hydrated,
  6. Use hand-held fans like fan-topped spray bottles to cool down your face,
  7. Use a desk-fan at work,
  8. Add short breaks to your schedule to avoid full depletion of your energy levels,
  9. Keep your freezer stocked with small ice packs, cold water bottles, neck wraps,
  10. Wear cooling vests or bras with cooling pads in,
  11. Wear lose-fitting, breathable white clothes in layers,
  12. Drink ice water with lemon, or cold iced tea, avoiding anything sugary,
  13. Chilly Pad, a $15 to $20 scarf-shaped piece of fabric that, once dampened, displays unique cooling properties. It can be draped around your neck, wrapped around your head or wrists, or laid across your legs to offer maximum cooling on the hottest parts of your body,
  14. TaTa Coolerz, developed by businesswoman Kim Gillespie. These cooling pads are, as you’d expect, worn concealed inside the bra.


If you or a loved one has MS, have a plan in place for staying cool, but also be ready for the unexpected. For example, a car break-down could leave you stranded with no way to cool down. A battery-powered spray bottle fan filled with water and tossed in the trunk might be all you need to keep Uhthoff’s Syndrome at bay.

History of Uhthoff’s Phenomenon/Sign

Among the various symptoms of MS, Wilhelm Uhthoff in 1890 described the peculiar phenomenon of ‘temporary worsening of symptoms with exercise’ in optic neuritis patients. Optic neuritis is a condition affecting the eyes. It is a common problem in many people with MS. Uhthoff noticed that visual symptoms were aggravated when people with MS performed exercise. While he attributed exercise to be the etiology of this problem, it was later realized that any action or condition that increases the core body temperature can worsen the symptoms in MS patients. This is called the Uhthoff’s phenomenon or Uhthoff’s sign.



©Willeke Van Eeckhoutte and Ireland, Multiple Sclerosis & Me, 2011-2015. Unauthorised use and/or duplication of this material without express and written permission from this blog’s author and/or owner are strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Willeke Van Eeckhoutte and Ireland, Multiple Sclerosis & Me with appropriate and specific direction to the original content.

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