Uhthoff’s phenomenon (also known as Uhthoff’s syndrome, Uhthoff’s sign, and Uhthoff’s symptom) is the worsening of neurologic symptoms in multiple sclerosis (MS) and other neurological, demyelinating conditions when the body gets overheated from hot weather, exercise, fever, or saunas and hot tubs. It is possibly due to the effect of increased temperature on nerve conduction. With an increased body temperature, nerve impulses are either blocked or slowed down in a damaged nerve but once the body temperature is normalized, signs and symptoms may disappear or improve.

UhthoffThis phenomenon was first described by Wilhelm Uhthoff in 1890 as a temporary worsening of vision with exercise in patients with optic neuritis. Later research revealed the link between neurological signs such as visual loss and increased heat production and Uhthoff’s belief that exercise was the etiology (etiology refers to the many factors coming together to cause an illness) of visual loss was replaced by the conclusions of these later researchers stating that heat was the prime etiology.

Anything Goes In Symptoms:

Many patients with MS experience increased fatigue and other symptoms such as pain, concentration difficulties, and urinary urgency, walking problems, memory issues, spasticity and more.  Literally most symptoms of MS may rear their ugly heads when exposed to heat. As a result, many patients with MS tend to avoid saunas, warm baths, hot tubs, hot showers, hot or hot and humid days or other sources of heat.

Peripheral nerve studies have shown that even a 0.5°C increase in body temperature can slow or block the conduction of nerve impulses in demyelinated nerves. With greater levels of demyelination, a smaller increase in temperature is needed to slow down the nerve impulse conduction. Exercising and performing activities of daily living can cause a significant increase in body temperature in individuals with MS, especially if their mechanical efficiency is poor due to the use of mobility aids, ataxia (dysfunction of the brain cerebellum),  weakness, and spasticity. The brain cerebellum is responsible for integrating a significant amount of neural information that is used to coordinate smoothly ongoing movements and to participate in motor planning.

However, exercise has been shown to be helpful in managing MS symptoms, reducing the risk of comorbidities, and promoting overall wellness. Thus while exercising staying cool while doing so and not overexerting oneself is important.  It’s knowing your limits and perhaps in time expanding those limits and thus making gains.

Uhthoff’s sign can be triggered by factors including the perimenstrual period, exercise, infection, fever, exposure to high ambient temperatures, and psychological stress

It is best to avoid temperature extremes with multiple sclerosis and important to have plans shoulda circumstance occur where you may be exposed to extreme temperatures.  For example many people with MS also report symptoms such as increased spasticity in cold temperatures.

Uhthoff’s sign is also sometimes called “a pseudo exacerbation” however that term is really not rightfully applicable because increased symptoms activity not associated with an flare up (exacerbation) can come from a variety of issues other than heat or cold for that matter.

A 2011 Swedish study reported that between 60% and 80% of people with MS experience heat sensitivity and symptoms.

Coping With Uhthoff’s Sign:

People who endure multiple sclerosis also may have a sensitivity to cold in addition to a sensitivity to heat.

cooler-vest Tips for coping with heat sensitivity:

  • Avoid going out on hot or hot humid days.
  • Wear a cooling vest or cooling device when outdoors.
  • Use air conditioning in your car, home or dwelling.
    • Central air conditioning is best however window or room based units can suffice.
  • Consider Geothermal home heat / cooling systems.
  • Use fans to remove heat from kitchen cooking distributing it better outdoors or through the house.
  • Use window fans if dwelling is hotter than outdoors.
  • Use fans to blow cooler air from basements upstairs.
  • Set up basement as a room that can be used when its too hot.
  • Use cooling products such as vests, neck wraps, and bandanas, during exercise or outdoor activity, or pre- and post-cool.
  • Icy drinks such as “slurpees” or popsicles can provide temporary relief.
  • Portable PoolUse a pool temperature under 85 de
  • Sprinkler’s or misting sprinklers can be helpful.
  • Small children’s pools or temporary pools can provide relief.
  • Cold gel packs and even frozen vegetables such as corn or peas in plastic bags can work as inexpensive cold packs.
  • Drink plenty of water to stay hydrated.
  • Wear lightweight breathable clothing that is a bright color (dark colors absorb more light hence heat, light colors reflect heat).
  • A cool bath or cool sponge bath can work wonders if you need find rapid relief.
  • Dry treatments, such as ice bags and chemical cold packs, may also used to lower body temperature.
  • Cool your car prior to driving.

Tips for coping with cold sensitivity:

  • Layer clothing as needed.
  • Take warm showers or baths.
  • Adjust heat dampers from your furnace to heat rooms better you are in as the day goes along.
  • Use portable heaters to enhance heat in rooms.
  • Warm up your car prior to driving.
  • Use thermal clothing.
  • Most body heat escapes from the head, you can wear a cap or wool or synthetic fibers hat indoors or outdoors.

Seeking Medical Attention:

If you have experienced Uhthoff’s before then you know what to expect.  It is important to not confuse Uhthoff’s sign to be associated with some other medical issue you are enduring.

Seek medical attention if:

  • You have not experienced heat-related symptoms of MS before.
  • If you are certain your current symptoms are not Uhthoff’s or MS related.
  • You have other symptoms appearing that you did not have before with heat or cold sensitivity.
  • If cooling down from heat or warming up from cold does not result in symptoms being mitigated back to where they were prior to exposure then seek medical attention.


Taking advantage of the cooling properties of water may help attenuate the consequences of heat sensitivity. In a study done by White et al. (2000), exercise pre-cooling via lower body immersion in water of 16-17°C (60-62 degrees fahrenheit) for 30 minutes allowed heat sensitive individuals with MS to exercise in greater comfort and with fewer side effects by minimizing body temperature increases during exercise. Hydrotherapy exercise in moderately cool water of 27-29°C (80-84 degrees fahrenheit) water can also be advantageous to individuals with MS. Temperatures lower than 27°C (80 degrees fahrenheit) are not recommended because of the increased risk of invoking spasticity.

It is important to know your limits in all respects with MS.  Heat, cold, exercise, stress and more.  One of the keys to making gains in MS are knowing your limitations, not pushing over the edge of those limitations but instead making small, steady gains.  For example, perhaps you know that you can exercise for 20 minutes however each time you attempt 30 minutes you start feeling symptoms.  Make little steps, move up to 21 or 22 minutes and over time try to continue to make gains.