Thanks for your posted question Inga.  Here is what we have on our site regarding heat and MS:

Cooling Methods - Body overheating causes demyelinated nerves to function less efficiently than usual. Although this effect is resolved within a few hours of regaining normal body temperature, active cooling can help reduce fatigue and improve stability. The following measures may be helpful:

• Use air conditioners in the summer
• Keep the home slightly cool in winter
• Avoid swimming in heated pools
• A portable helmet that uses cold liquid to cool the head and neck and therefore lower core body temperatures may help MS symptoms during daily activities
• Cooling suits are being investigate

As well:

• Exercise programs must be designed to stimulate working muscles, but at the same time avoid overload and overheating, which can block nerve conduction.

You can read about these and more lifestyle changes in our Living with MS section.

Hope this helps - all the best, sue

Hey Inga

Just had to chime in here.  My personal experience is not good with saunas.  In the months prior to my diagnosis I sat in a sauna at my gym.  It was just some minutes before I felt fatigued and dizzy and had blurry vision.  I vowed to never try that again!  But everyone is different so it might not bother you.  Heat absolutely has an effect on my symptoms.

Thank you for your question and I do hope you return to Health Central.