What Is the Uhthoff Phenomenon?

Medically Reviewed by Christopher Melinosky, MD on March 07, 2024
3 min read

Uhthoff’s phenomenon is most commonly a symptom of multiple sclerosis (MS), though it can also coincide with other optic nerve disorders. It is characterized by a temporary worsening of MS symptoms when your body’s temperature is raised by fever, exercise, or using a hot tub or sauna. Usually, the phenomenon lasts less than 24 hours.

Uhthoff's phenomenon, or syndrome, was discovered in 1890 by a German neuro-ophthalmologist who studied the worsening of MS symptoms when the body’s temperature was raised. He first described it as difficulty seeing when somebody was exercising.

It has since been discovered that Uhthoff’s phenomenon is triggered more by the body temperature being raised generally than by simply exercising. It has also been shown that Uhthoff's phenomenon causes more symptoms than eyesight interference. The exact mechanism that causes heat-related vision problems is also responsible for other multiple sclerosis symptoms.

Some of the factors that people speculate cause Uhthoff’s phenomenon are:

  • Blockage of ion channels 
  • Heat shock proteins 
  • Circulatory changes
  • Serum calcium 
  • Unidentified humoral substances 

Typically the actions that cause Uhthoff’s phenomenon are:

  • Menstrual period-related temperature changes
  • Exercise 
  • Fever
  • Sun-tanning
  • Hot showers
  • Sauna
  • Psychological stress
  • Hot meals 
  • Smoking
  • Central heating

It hasn’t been fully understood exactly what causes these changes in the body. Many speculate that it has to do with nerves within the central nervous system changing when temperatures get hotter. It has been found that Uhthoff's signs in the body can be reduced when you actively attempt to cool your body down. 

In the 1950s, scientists invented a test for multiple sclerosis in which you would get into a hot bath and raise your body’s temperature. While other tests used today, it linked MS and Uhthoff's phenomenon. Between 60% and 80% of all people with multiple sclerosis will have Uhthoff’s phenomenon, as well.

Uhthoff's syndrome is always temporary. It can be differentiated from a full MS relapse because its symptoms stop when your body returns to a more normal temperature. It is just a symptom and does not mean that your MS has progressed any further or that you will have any permanent damage. 

Uhthoff’s phenomenon symptoms are:

  • Visual issues
  • Fatigue 
  • Pain
  • Balance issues
  • Weakness
  • Bladder problems 
  • Cognitive changes
  • Sensory changes

Uhthoff's phenomenon does not occur in everyone with MS; some people have never experienced it.

There is no treatment for Unthoff’s phenomenon, but it can be managed in these ways:

  • Find things that cool your body from the outside, like clothing, shade, sprays, or other products. 
  • Drink or eat cool things like ice water, ice cubes, or frozen fruit smoothies.
  • Avoid the direct sun or hot temperatures whenever you can. 
  • When you exercise, stay in the shade, drink lots of cold water, and rest whenever you can. 
  • Exercise by swimming in a cooler-temperature swimming pool.
  • Wear loose-fitting and breathable clothing. 
  • Take cold baths and showers to help give you energy. 
  • Try to stick to eating cooler foods. 
  • Install a fan, air conditioner, or evaporative cooler in your house. 
  • Keep central heating at a low temperature or avoid using it.
  • If you take hot baths or showers, start them off at a cooler temperature. 
  • Close your blinds or curtains to avoid letting direct sunlight into your home. 

Usually, your symptoms will go away in a period of minutes, up to an hour, once you remove the thing that is making your body temperature high or after you effectively cool yourself down. If you have had Uhthoff's syndrome in the past, you should not take hot showers, saunas, or go in hot water. 

If you have very severe symptoms, a doctor will sometimes recommend taking a medication called 4-aminopyridine. This medication will help maintain the proper potassium channel blocker levels and help stabilize your nervous system. In addition, these properties help to reduce any visual symptoms you might have. 

Your doctor might also prescribe you a medication called dalfampridine which helps to treat MS generally. However, the best treatment for MS is to treat and manage your underlying multiple sclerosis. Becoming attuned to your body and how it reacts to various things will help you avoid symptoms of Uhthoff's phenomenon in future.