Many people with MS who are heat sensitive may experience a temporary worsening of symptoms when the weather is very hot or humid, sunbathe, get overheated from exercise, or take very hot showers or baths. Some people may notice that their vision becomes blurred when they get overheated—a phenomenon known as Uhthoff's sign. Even a slight elevation in core body temperature of one degree can cause a temporary increase in MS symptoms.
These temporary changes in
symptoms are called pseudoexacerbations which look like and act like
real relapses, but are temporary and do not indicate disease activity or
progression. Realize that when we talk about pseudoexacerbations, we
are certainly speaking of very real symptoms as there’s nothing “fake”
about the experience; it is just temporary. Common triggers that may
cause a pseudoexacerbation include infection, especially urinary tract
infection, stress, pain or fatigue, exposure to heat or cold,
premenstrual syndrome, or certain medications.
Read this post in its entirety:
What is an MS Relapse versus a Pseudoexacerbation?