global view constructed of white lines
women sitting in a pool with a hat on
May 26, 2020

A Hot Topic: The Effects of Heat in Persons with Multiple Sclerosis

by Barbara Giesser

It has long been observed that most persons with Multiple Sclerosis (MS) are very sensitive to the effects of overheating. One hundred years ago, the way persons with MS were diagnosed was to put them in a bath containing hot water, the “hot bath test”. If they became weak or developed other neurologic symptoms, this was taken as evidence that they had MS.

How Does Heat Effect MS?

The basic problem in Multiple Sclerosis is that nerves are damaged and are not able to conduct chemical and electrical signals in an efficient and coordinated manner. If a damaged nerve becomes heated, it causes further difficulty with electrical transmission. Importantly, the heat does not cause more or new damage to the nerve itself, but temporarily impedes its ability to function.

This is why many persons with MS may notice a temporary worsening of symptoms if they have a fever, or become overheated through exertion, or are in a heated environment. This is known as a “pseudoexacerbation”, i.e. an MS flare-up that is due to a known precipitant, in this case, heat. Generally, when the person cools down, the symptoms improve.

Tips To Stay Cool This Summer For Those With MS

When going outside, wear a hat, stay hydrated, and use cooling strategies

  • There are cooling towels and bandanas that can be made to stay moist and cold, and which will rapidly cool someone down when placed on the head or neck.
  • There are vests that have pockets into which cold packs can be placed, and worn if prolonged heat exposure is a concern.  
  • A small portable pocket fan may also help. These same strategies can be used when exercising.

Keeping Cool Inside

Inside, fans and air conditioning are helpful. For persons with medical conditions that require consistent indoor heating or cooling, there are allowances that can be obtained from the power company.

Exercising and Keeping Cool

Swimming is a great exercise because the water dissipates heat. It is recommended that the pool not be heated to more than about 85 degrees.

In general, persons with Multiple Sclerosis should avoid hot tubs and saunas.


For more information or to schedule an appointment, contact us at 310-582-7613.

About the Author

Barbara Giesser, MD

Barbara Giesser

Barbara S. Giesser, MD, FAAN, FANA, is an internationally recognized clinician and award-winning educator who has specialized in the care of persons with Multiple Sclerosis since 1982. Her approach to the diagnosis and management of persons with MS combines advanced diagnostics and a personalized medication plan for each patient with an emphasis on integrating lifestyle and wellness strategies into the neurologic treatment plan.

Last updated: May 27th, 2020