People with multiple sclerosis (MS) often experience a temporary worsening of their symptoms in hot weather or when they run a fever. These temporary changes can result from as little as one-quarter to one-half of a degree elevation in core body temperature, as an elevated temperature further impairs the ability of demyelinated nerves to conduct electrical impulses.

3:013 Women Share Their Experiences Managing MS in the Heat

3:01

3 Women Share Their Experiences Managing MS in the Heat

Symptoms

Numbness in the extremitiesFatigueBlurred visionTremorWeaknessCognitive problems

Heat intolerance can also differ in terms of:

Verywell / Emily Roberts

Symptoms of Heat Intolerance in Multiple Sclerosis

Causes

MS can result in demyelinating plaques in the brain, optic nerves, and spinal cord. This slows the ability of the affected areas to function, and heat further slows down nerve impulse transmission in these regions.

Typically heat worsens symptoms that the person has previously had before. So if they had an MS flare where they had numbness which later improved, the heat may bring out those symptoms again since the myelin is not fully repaired and the heat is a stressor.

A worsening of symptoms as a result of becoming overheated (with the most common one being blurred vision) is a phenomenon known asUhthoff’s sign.

Increased activity, hot weather, hot baths and showers, saunas, and hot tubs are all sources of heat that can cause issues for someone living with MS.

These sources can trigger a phenomenon known as anMS pseudoexacerbation, which is the experience of having symptoms appear or worsen due to heat exposure.

It’s important to understand that this is different from a truerelapse. In the case of a pseudo-exacerbation, when the body’s temperature returns to normal, MS symptoms disappear. Fortunately, no damage—such as inflammation, loss of myelin, or new lesions—occurs during such an episode.

Did You Know?Before there were more sophisticated screening tests for MS, the “hot bath test” was used todiagnose MS. A person suspected of having MS was immersed in a hot tub of water and watched to see if neurologic symptoms appeared or got worse.

Did You Know?

Before there were more sophisticated screening tests for MS, the “hot bath test” was used todiagnose MS. A person suspected of having MS was immersed in a hot tub of water and watched to see if neurologic symptoms appeared or got worse.

Treatment

Worsening of symptoms in the heat is temporary, and they resolve when the body cools down. Simple cooling techniques usually do the trick.

Here’s what you can do to cool off:

A Word From Verywell

While heat intolerance can be extremely debilitating, the good news is that there are simple ways to manage it. Those who are unable to function well at even slightly elevated temperatures may want to consider moving to a cooler geographic location. For most, though, simple strategies are enough to ease heat-related symptoms.

Frequently Asked Questions

Yes. Many people with multiple sclerosis (MS) have heat intolerance that causes their symptoms to worsen temporarily. These symptoms often appear in the form of fatigue, tremors, or weakness, but a heat intolerance can cause any old or new MS symptom to occur. Cold temperatures can also be an issue for some people with MS.

Learn MoreHow Multiple Sclerosis Is Treated

5 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Flensner G, Ek AC, Söderhamn O, Landtblom AM.Sensitivity to heat in MS patients: a factor strongly influencing symptomology–an explorative survey.BMC Neurol. 2011;11:27. doi:10.1186/1471-2377-11-27Davis SL, Wilson TE, White AT, Frohman EM.Thermoregulation in multiple sclerosis.Journal of Applied Physiology. 2010;109(5):1531-1537. doi:10.1152/japplphysiol.00460.2010Ontaneda D, Rae-Grant AD.Management of acute exacerbations in multiple sclerosis.Ann Indian Acad Neurol. 2009;12(4):264–272. doi:10.4103/0972-2327.58283National Multiple Sclerosis Society.Heat and temperature sensitivity in multiple sclerosis.Cleveland Clinic.Multiple sclerosis (MS).

5 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Flensner G, Ek AC, Söderhamn O, Landtblom AM.Sensitivity to heat in MS patients: a factor strongly influencing symptomology–an explorative survey.BMC Neurol. 2011;11:27. doi:10.1186/1471-2377-11-27Davis SL, Wilson TE, White AT, Frohman EM.Thermoregulation in multiple sclerosis.Journal of Applied Physiology. 2010;109(5):1531-1537. doi:10.1152/japplphysiol.00460.2010Ontaneda D, Rae-Grant AD.Management of acute exacerbations in multiple sclerosis.Ann Indian Acad Neurol. 2009;12(4):264–272. doi:10.4103/0972-2327.58283National Multiple Sclerosis Society.Heat and temperature sensitivity in multiple sclerosis.Cleveland Clinic.Multiple sclerosis (MS).

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Flensner G, Ek AC, Söderhamn O, Landtblom AM.Sensitivity to heat in MS patients: a factor strongly influencing symptomology–an explorative survey.BMC Neurol. 2011;11:27. doi:10.1186/1471-2377-11-27Davis SL, Wilson TE, White AT, Frohman EM.Thermoregulation in multiple sclerosis.Journal of Applied Physiology. 2010;109(5):1531-1537. doi:10.1152/japplphysiol.00460.2010Ontaneda D, Rae-Grant AD.Management of acute exacerbations in multiple sclerosis.Ann Indian Acad Neurol. 2009;12(4):264–272. doi:10.4103/0972-2327.58283National Multiple Sclerosis Society.Heat and temperature sensitivity in multiple sclerosis.Cleveland Clinic.Multiple sclerosis (MS).

Flensner G, Ek AC, Söderhamn O, Landtblom AM.Sensitivity to heat in MS patients: a factor strongly influencing symptomology–an explorative survey.BMC Neurol. 2011;11:27. doi:10.1186/1471-2377-11-27

Davis SL, Wilson TE, White AT, Frohman EM.Thermoregulation in multiple sclerosis.Journal of Applied Physiology. 2010;109(5):1531-1537. doi:10.1152/japplphysiol.00460.2010

Ontaneda D, Rae-Grant AD.Management of acute exacerbations in multiple sclerosis.Ann Indian Acad Neurol. 2009;12(4):264–272. doi:10.4103/0972-2327.58283

National Multiple Sclerosis Society.Heat and temperature sensitivity in multiple sclerosis.

Cleveland Clinic.Multiple sclerosis (MS).

Meet Our Medical Expert Board

Share Feedback

Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit

Was this page helpful?

Thanks for your feedback!

What is your feedback?OtherHelpfulReport an ErrorSubmit

What is your feedback?