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Keep Cool: Multiple Sclerosis and Heat Tolerance

Jacqueline A. Hall, MS, OTR/L, MSCS
VA Puget Sound Health Care System – Seattle

(See Links to Additional Information and Products at the end of the article.)

Often after someone develops multiple sclerosis (MS), it is not unusual to develop heat intolerance. Small increases – as little as ½ºF – in core body temperature can increase MS symptoms. The cause of this is that 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 the 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 body temperature to rise – some we usually think of, and some 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 for some an increase in MS symptoms. A not so obvious cause of increased body heat is having a fever.

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. Causes that are not too obvious would be things such as wearing clothing that keeps you too warm, or being in rooms that although they are comfortable for others are too warm for you. Medical illnesses such as bladder infections, colds, and/or the flu might cause you to experience a low to medium grade fever, which in turn increases your core body temperature.

Keeping Cool

If heat affects you, you need to take extra precautions and use strategies to keep cool. There are a number of ways you can help your body to stay cool and keep yourself healthy.

Adjust the temperature in your environment

o    Use an air conditioner or fan in the room you are working in, or in your vehicle when traveling

o    Rest in rooms that are out of direct sunlight or have adequate shading over windows that have a West or Southern exposure

o    When showering or bathing, turn the fan on in the bathroom and/or open a window if possible to help circulate the room air;

o    Make sure the water temperature in your shower or bathtub is significantly lower than your body temperature;

o    Take a cool bath

o    Wear layered clothing that can be removed as necessary to adjust your body temperature

o    Avoid traveling to warm parts of the country or world during their hot and/or humid seasons

o    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 still remain hydrated. Here are some tips for better hydration:

o    Place a plastic bottle of water in the freezer until frozen. Place this by your bedside at night to have cold water available to drink without having to get out of bed.

o    Drink chilled water, juices, ices, and popsicles throughout the day to help keep your body temperature down.

o    Avoid drinks with caffeine (e.g. Sodas, colas, coffee, tea, chocolate, and some energy drinks) are diuretics, so you 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

o   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.

o   Use an umbrella while out in the sun.

o   Wear a vented hat, sunglasses, and use sunblock while outdoors. (The sunblock won’t reflect heat, but will help prevent you from skin cancer.)

o   Use a cooling vest (see below).

o   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, then allow 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. Here are some tips:

o   Take a cool bath before working around the house or in the garden.

o   Avoid hot or heavy meals especially before going outside.

o   Stay inside during the midday warmer hours.

o   Take a shower in a swimsuit before working outside in it (the moisture in your suit will help cool you).

o   Exercise or complete home management activities in the morning (during the cool time of the day). 

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.

What are the different types of cooling vests?

o   Active cooling: requires an electricity source to operate the equipment that circulates air through the vest

o   Passive cooling: no working components; portable
§  Gel inserts and ice packs
§  Phase change – non-freezing, cooling liquid in packs
§  Embedded hydrogel crystals
§  Ice-chilled recirculating water
§  Evaporative cooling – best in low humidity/arid environments

We have covered some of the important information on how to keep yourself healthy if you are someone who is affected by heat. You will need to discuss your heat tolerance problems with your healthcare provider to address the appropriate strategy for you. The VA generally covers adaptive devices like cooling vests to help people with MS manage their symptoms. If you experience heat intolerance contact your VA medical team which includes your primary care physician, neurologist, occupational therapist and others to find the best solution for your needs.

Links to Additional Information

Below are some Internet resources you may find helpful as you work on discovering what works best for you: 

MSAA (MS Association of America)

MSF (MS Foundation)

NMSS (National MS Society)


Glacier Tek

Arctic Heat USA

Heat Relief Depot

Polar Products

StaCool Vest


  Active MSers

These websites are provided as a convenience to begin your Internet search about MS cooling strategies. The VA does not endorse any products that are advertised on these websites. We recommend that you review the information and products with your healthcare provider before deciding what will meet your medical needs.


Updated: July 2016