Uhthoff’s Phenomenon: MS Heat Intolerance

Now that we’re heading into the hot summer months in most parts of the United States, I want to talk about why multiple sclerosis symptoms worsen in the summer heat!

First described by Wilhelm Uhthoff in 1890 the temporary worsening of vision and other neurologic symptoms when the body is overheated is now known as the Uhthoff Phenomenon or Uhthoff’s symptoms.

Our bodies overheat not only from the outside temperature rising, also from fever, exercise, saunas and hot tubs.

MS heat intolerance symptoms can result from a very slight rise in core body temperature even as little as one-quarter to one-half of a degree. An elevated temperature further impairs the ability of a demyelinated nerve to conduct electrical impulses.

The Uhthoff Phenomenon

Uhthoff’s Symptom also referred to as Uhthoff’s Phenomenon was the principal diagnostic test for multiple sclerosis until the 1980’s when more accurate test methods became available.
An increase in heat can worsen many MS symptoms and cause new ones to appear but is most often seen to exacerbate MS fatigue.


• Wearing a cooling vest
• Wearing a cooling necklace
• Cool bath or shower

I’d love to hear what you do to stay cool in the summer heat~

You know I’m living in the cool climate of Alaska but it will only be a few years until we move to the heat of northern Utah!


About our Co-Founder: With a bachelors in Social Work, Linda is 53 years old, happily married with eight children and 17 grandchildren. Diagnosed with MS in 1995 and now having accepted and truly embraced her new reality, Linda has created MSrelief.com. She is dedicated to proving that joy can be chosen while living with Multiple Sclerosis. Linda specializes in helping others, especially those with MS attain the lifestyle, independence and happiness amid living with MS.


  1. Last summer I saw many of my friends suffered from Multiple Sclerosis symptoms. Fortunately during the summer I always try to take ice bath which helps a lot. Thanks for your precious tips.

    • Claudia,
      I baths~ WOW! I have hard time even taking a cool shower! Does this mean you have MS too?

      • Unfortunately ‘YES’ 🙁

        • ICE BATH??!!! As in fully submersed in icy water??!!! Holy cow Claudia, you’re a brave soul! ROFL… I think I’ll stick to the air conditioned house. As an additional strategy, I often run my wrists under really cold water for a few minutes. My theory is that I’m cooling my circulatory system and then hopefully positively effecting my core temp. Is it possible to measure our core temp?

  2. In summer you lose so much water of your body . . You got so much dehydration but you have to consume good amount of liquid in drink to energize yourself !

    • Hey Fitness Republic, I look forward to knowing your name! Yes! Dehydration is a serious problem! People often don’t realize that soda and other drinks are diuretics and they need to drink two times the water to make up for what they lost during their soda drinking!

  3. I stay indoors when the heat is simply terrible (with the HVAC in full blast, always making sure HVAC is working without any issues). Would fix myself a glass of nice freshly squeezed orange juice and read a good book. I have never actually tried wearing a cooling vest, but now that you’ve mentioned it, then I may just have to consider that.

  4. Hello,

    I’ m currently having problems with uhthoff phenomenon, had it for 6 weeks now since i had a relapse which caused optic neuritus. My question is.. does it ever go by that i mean does it ever fully clear up / go away, or am i stuck with it for the rest of my life, searching the web i can’t seem to find the answer to this question.

    Thanks in advance

    • Brian,
      I wish I could say I know the answer! Unfortunately I’m not a doctor, just a woman with MS! And even more unfortunate is when you ask your doctor, you’ll probably hear, “It’s different for everyone!” I know as I’ve talked to others living in the heat, that they do different things to cool down and when they do, the symptoms sometimes go away. My friend told me just the other day that she uses a cooling blanket that helps her stay cool. We are working with 1-800Wheel chair and they have a cooling pad. It’s only $7 and it looks like it would be a great way to lower your core temperature. You can order a cooling pad by copying and pasting this link in your URL: http://www.1800wheelchair.com/product/5617/jobar-gel-cooling-pad?kbid=1744

      I hope you can cool yourself enough to cut down your symptoms!

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