Why Exactly Does Heat Trigger Pain in Multiple Sclerosis Patients?

It is well-known that heat, in many forms, is an issue for MS patients. In fact, this notion was established as early as the late 19th century through the introduction of the hot bath test. In the days before medical scans, diagnosing MS was done by immersing an individual in a bath of warm water and seeing if their neurological symptoms appeared or worsened. Although this test has not been used for quite a while, it is worth mentioning for those who find that their symptoms worsen when they take a hot bath or shower.

Recent evidence shows that 60-80% of people with MS experience worsening of their existing symptoms, as well as the onset of new painful symptoms when exposed to elevated temperatures. Standing outside in hot or humid weather, exercising, taking a hot shower or bath, tanning, or running a fever are all associated with a rise in body temperature that can aggravate MS symptoms and trigger new ones.

But what is it exactly that causes this disturbing and unfortunate sensitivity to heat?

MS and heat sensitivity

Health experts believe that the reason people with MS are sensitive to heat is due to a disturbance or blockage in the normal nerve conduction process. A rise in body temperature causes the nerves to create electric signals within the body in a less efficient manner, especially if the nerve fibers have already been damaged by the disease. Since damaged nerve fibers already transmit messages to and from the brain at a slower rate, heat further hinders this communication between the brain and the spinal cord. Heat can also trigger the onset of lesions on the brain area that is responsible for regulating body temperature. Either way, poor communication can aggravate MS symptoms.

Although unpleasant, the worsening of MS symptoms triggered by heat is usually temporary and symptoms tend to ease once the nerve fibers have had a chance to (literally) cool down.

Elevated temperatures worsen MS symptoms 

A majority of MS symptoms are brought about by damage to the nerves and with elevated temperatures, the symptoms (including heightened fatigue, blurry vision, loss of balance or decreased concentration) are commonly worsened. “The nerve impulses cannot travel efficiently, and fatigue sets in. The dangers of heat intolerance might include a temporary decrease in balance, strength, feeling, or vision, which could lead to falls and other problems,” said Dr. Jack Burks, chief medical officer of the Multiple Sclerosis Association of America.

Read on to learn more about how to manage heat sensitivity in MS.