Heat Sensitivity

Heat Sensitivity in MS

When someone with MS experiences an increase in temperature, which in turn causes a temporary worsening of one or more symptoms, this is known as “heat sensitivity in MS.” A person’s temperature may increase as a result of exercise or other physical exertion, being in a hot and/or humid environment (which includes taking a hot bath or shower), and fever.1

The most common symptoms reported with heat sensitivity in MS are blurred vision and increased fatigue, weakness, and incoordination. Sometimes speech and cognition are also affected, and this can include a slurring of one’s words and the inability to think quickly or clearly.

As many as 80% of individuals with MS experience heat sensitivity, which was first recognized in the late 1800s by Wilhelm Uhthoff, a German ophthalmologist who specialized in neurologic disorders. He observed that patients with MS and other demyelinating conditions developed blurry vision while exercising. He also found that once the patients cooled down, their vision returned to normal. This manifestation of heat intolerance became known as “Uhthoff’s phenomena” and this term is still sometimes used to describe the worsening of any MS symptom resulting from heat intolerance.1


The Causes of Heat Sensitivity in MS


Tips to Reduce or Avoid Heat Sensitivity


Sensitivity to Cold in MS


References


Updated in June 2025


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