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Keep Cool: Multiple Sclerosis and Heat Tolerance

Jacqueline A. Hall, MS, OTR/L, MSCS -- Seattle, WA

People with MS often have a low tolerance for changes in their body temperature caused by the air temperature, activity, digestion, or metabolic changes. Small increases – as little as ½ºF – in core body temperature can increase MS symptoms. Nerves that have lost their conductive coating (myelin sheath) become more sensitive to heat, and the nerve signal slows down or is blocked, resulting in an increase in symptoms. Depending on the location of the nerve damage in your body, symptoms may include increased heart rate, sweating, dizziness, muscle weakness, slowed reaction times, reduced energy, and difficulties with attention and concentration.

Causes of Increased Body Heat

Many things can cause your body temperature to rise – some we usually think of, and some that are a little harder to see. Obvious causes of increased body temperature are things such as being in a warm environment, increasing physical activity, or wearing too many clothes. All these can easily lead to increased body temperature and an increase in MS symptoms. Less obvious causes of increased body heat include having a fever, changes in metabolism, hormonal changes, or side effects of medications.

Warm environments may include things such as your kitchen during meal preparation, working hard around your home (whether cleaning the house or working outdoors), taking a hot shower, swimming in a warm pool, or being out in the sun. Your body temperature may also rise with increased physical activity, such as when walking, propelling your wheelchair, exercising, or doing other leisure activities. Wearing clothing that keeps you too warm, or being in rooms that, although they are comfortable for others, are too warm for you may also increase your body temperature. Medical illnesses contributing to higher core body temperature may include bladder infections, colds, and the flu (causing a low to medium grade fever).

Keeping Cool

If heat affects you, you need to take extra precautions and use strategies to keep cool. Minimizing your symptoms will help reduce the need for additional medications and maximize your independence and safety. There are several ways you can help your body to stay cool and keep yourself healthy.

Adjust the temperature in your environment

  • Use an air conditioner or fan in the room you are working in, or in your vehicle when traveling.
  • Rest in rooms that are out of direct sunlight or have adequate shading over windows that have a western or southern exposure.
  • When showering or bathing, turn the fan on in the bathroom and/or open a window if possible to help circulate the room air.
  • Make sure the water temperature in your shower or bathtub is significantly lower than your body temperature and/or take a cool bath.
  • Wear layered clothing that can be removed as necessary to adjust your body temperature.
  • Avoid traveling to warm destinations during their hot and/or humid seasons.

When you feel hot, use a spray bottle to mist yourself with water at regular intervals during activity (or even when sitting) – as many people with MS lose the ability to perspire and release body heat.

Drink plenty of fluids

During periods of increased activity, your body can generate several times the amount of heat it does at rest. The body releases excess heat by sweating and evaporation. Adequate water intake is important to be able to perspire during exercise and remain hydrated. Below are some tips for better hydration.

  • Place a plastic bottle of water in the freezer until frozen. Put the bottle by your bedside at night so that you have cold water available to drink without having to get out of bed.
  • Drink chilled water, juices, and popsicles throughout the day to help keep your body temperature down.
  • Avoid drinks with caffeine (e.g. sodas, colas, coffee, tea, chocolate, and some energy drinks). Caffeinated drinks are diuretics, causing you to lose fluid by increased urination. This leaves less fluid in your body to sweat (one of our natural ways of cooling down).

Use cooling equipment

  • Layer up with lightweight, breathable clothes. Remove the layers as necessary to keep cool. Look for clothing that is designed to have more air flow through it, making it cooler to wear.
  • Use an umbrella while out in the sun.
  • Wear a vented hat, sunglasses, and use sunblock while outdoors. (The sunblock won’t reflect heat, but will help prevent you from skin cancer.)
  • Use a cooling vest (see below).
  • Use cooling packs on your wrists, neck, and on your head (under a hat). Another strategy is to wear cloth-type hats and dip them in water, allowing the sun to evaporate the water, cooling your head.

Develop a personal cooling program

Research studies show that individuals who take a cool bath or shower (not cold), sit in an air-conditioned room, or wear a cooling vest for 45 minutes a day have an overall decrease in their core body temperature. This results in an improvement in strength and less fatigue for up to 2 hours after cooling. Below are some tips.

  • Take a cool bath before working around the house or in the garden.
  • Avoid hot or heavy meals, especially before going outside.
  • Stay inside during the midday warmer hours.
  • Take a shower in a swimsuit before working outside in it. The moisture in your suit will help cool you.
  • Exercise or complete home management activities in the morning, the cooler time of the day.

Cooling Vests

The above strategies work well for most people, but this doesn’t mean that you will never have problems maintaining your body core temperature. When the “low-tech” methods (above) aren’t adequate, a cooling vest might meet your needs.

How does a cooling vest work?

A cooling vest is designed to keep the body’s core temperature (around the heart and spinal cord) within safe levels to reduce symptoms of heat intolerance. The vest absorbs body heat, evaporates perspiration, and conducts cooler temperatures to the body through the skin. Cold packs for the neck, wrists, and head conduct cold through to the arteries, cooling the blood circulating in the body.

When should I wear a cooling vest?

The cooling vest should be worn in warm-to-hot conditions or when physical activity is planned. The vest can help keep you cool up to 3 hours when worn correctly, although this can depend on things such as environmental temperature, humidity, and your level of activity.

How do I use the cooling vest?

It is beneficial to wear the cooling vest at least 30 minutes prior to physical activity. The cooling vest is more effective when worn over thin clothing and, when needed, when breathable fabrics are worn over the vest.

The vest usually has up to six Velcro closure pockets to house the cooling packs, 2-4 pockets on the front and 3-4 pockets on the back. Place each cooling pack into one of the pockets on the vest. Put the vest on and close the front. Adjust the side straps to provide a snug but comfortable fit with the cold packs in place.

Are there different types of cooling vests?

An excellent summary of different cooling vests and what are recommended for MS can be found at Active MSers.

  • Active cooling: requires an electricity source to operate the equipment that circulates air through the vest.
  • Passive cooling: portable with no working components (e.g. gel inserts and ice packs, phase change – non-freezing, cooling liquid in packs, embedded hydrogel crystals, and evaporative cooling – best in low humidity/arid environments).

How do traditional cooling pack vests work?

Initially, cooling packs should be put in the freezer overnight. Re-cooling them after use takes 30-60 minutes in the freezer. It does not harm the cooling packs to store them in the freezer. You will need to experiment to determine which level of cooling you can tolerate and is most beneficial to you. Some cooling vests have sleeves that cover the cooling packs and provide insulation. Layering clothing can help regulate the vest temperature to your comfort.


If you are someone who has an increase in your MS symptoms when your body is overheated, it is important to use some of these methods to keep cool. If you experience heat intolerance contact your VA medical team which includes your primary care physician, neurologist, rehabilitation physician, or occupational therapist to find the best solution for your needs. The VA may provide adaptive equipment such as cooling vests to help you manage your symptoms.

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