What should you know about MS and heat tolerance?

A rise in body temperature can slow the movement of signals along nerves affected by MS. This may make existing symptoms more noticeable during hot weather, exercise, fever, hot baths, or a warm room. The change often improves after cooling and does not necessarily mean that MS is progressing.

Heat intolerance is also a symptom with other possible explanations, including dehydration, infection, thyroid overactivity, or excess body weight. Heat exhaustion can become serious, especially when sweating, dizziness, headache, nausea, or confusion develops.

Plan activity for cooler parts of the day, take regular breaks, drink fluids, use fans or air conditioning, and choose light, breathable clothing. A cool shower, damp cloth, or cooling vest may help. Reduce exertion if vision, balance, or strength changes in the heat, and record what triggers symptoms and how quickly they settle.

Seek urgent help for confusion, fainting, severe weakness, inability to drink, trouble breathing, or a very high temperature after heat exposure. Contact your MS team or clinician if symptoms are new, persist after cooling, follow an infection, or interfere with walking, vision, or daily tasks.

Ask whether a medication, infection, or another condition could be increasing heat sensitivity; which cooling strategies fit your treatment plan; and how to distinguish a temporary heat-related change from a relapse.