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Heat & Temperature Sensitivity


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For many years, the “hot bath” test was used to diagnose multiple sclerosis. A person suspected of having MS was immersed in a hot tub of water, and the appearance of or worsening neurologic symptoms was taken as evidence the person had MS.

Many people with MS experience a temporary worsening of their symptoms when the weather is very hot or humid, or when they run a fever. These temporary changes can result from even a slight elevation in core body temperature (one-quarter to one-half of a degree). An elevated temperature further impairs the ability of a demyelinated nerve to conduct electrical impulses.

Activities including sunbathing, exercise, and taking very hot showers or baths can have the same effect. For example, some people notice their vision becomes blurred when they get overheated — a phenomenon known as Uhthoff's sign.

Heat-related symptoms are temporary

Heat generally produces only temporary worsening of symptoms. It does not cause more disease activity (demyelination or damage to the nerves themselves). The symptoms generally reverse quickly when the source of increased temperature is removed.

Strategies for easing the effects of heat

  • Stay in an air-conditioned environment during periods of extreme heat and humidity. If an air conditioner is needed to help minimize symptoms, the cost of this equipment may be tax deductible if the physician has written a prescription for it.
  • Use cooling products such as vests, neck wraps, and bandana  during exercise or outdoor activity.
  • Wear lightweight, loose, breathable clothing.
  • Icy drinks or popsicles can provide temporary relief.
  • Use an oscillating fan or air conditioning during indoor exercise.
  • Exercise in a cool pool (<85 degrees) or a cool environment. If you are exercising outside, pick cooler times of the day, usually early morning or evening.
  • Try pre- and post-cooling to decrease the heating effects of exercise. Get into a bathtub of cool water and continue adding cooler water over a period of 20 to 30 minutes. A cool bath or shower can also help reduce core body temperature following activity or exposure to a hot environment.

Please see below for a list of approved cooling product vendors.

Cold can also be a problem

Some people with MS notice that symptoms, particularly spasticity, become worse in cold weather. It is generally recommended that people with MS who are sensitive to temperature try to avoid extremes of either hot or cold. Anyone considering a move to a "better" climate should visit first to see if the climate change is, indeed, beneficial.

Moving for optimal climate

Anyone considering a move to a "better" climate should first make a long visit to see if the climate change is indeed beneficial. You may have to change your plans if the weather seriously worsens symptoms after a visit.

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