Hot weather and Multiple Sclerosis

Weather is considered a possible influence on a wide variety of health conditions by weather factors may make existing pain worse. Some people with MS report that their symptoms get worse in hot weather or when they become overheated. Heat intolerance in MS shows up as a "pseudoexacerbation" -- the experience of having symptoms appear or worsen due to heat exposure. This is different than a true relapse. A True relapse is an exacerbation (also known as an attack, a relapse, or a flare) is a sudden worsening of an MS symptom or symptoms, or the appearance of new symptoms, which lasts at least 24 hours and is separated from a previous exacerbation by at least one month. The most common disease course in MS, called relapsing-remitting MS, is characterized by clearly defined acute exacerbations, followed by complete or partial recovery with no progression of the disease between attacks.

In the case of a pseudoexacerbation, when the body’s temperature returns to normal, these symptoms disappear. No damage, such as inflammation, demyelination or new lesions, has been done during these pseudoexacerbations. It's important to remember that summer's heat could trigger a brief pseudo-relapse. While the symptoms are real enough, they are temporary and subside when the triggering event, such as heat, has passed." Once the triggering event is past—e.g., the body temperature returns to normal, the symptoms subside as well. Some people with MS report a worsening of their symptoms during or after periods of intense stress.