MS and Heat

Last updated Aug. 22, 2022, by Marisa Wexler, MS

Fact-checked by Ines Martins, PhD

People with MS may find that their symptoms worsen with higher temperatures

FAQs about heat intolerance and MS

No. Exposure to extreme heat can result in a temporary worsening of multiple sclerosis (MS) symptoms, but this phenomenon is different from a true relapse. MS relapses are caused by increases in disease activity that last for at least 24 hours. In contrast, the pseudo-exacerbations that occur due to temperature sensitivity are not caused by disease progression and resolve after body temperature is restored.

Sunlight exposure is associated with a lower risk of developing multiple sclerosis and has also been shown to reduce disease severity in people with the condition. This protective effect is believed to be mainly mediated by vitamin D, which is produced in the skin upon exposure to sunlight and is important for modulating immune system activity. However, MS patients with heat sensitivity, and those whose symptoms and medications may increase sun sensitivity, should avoid sunbathing and direct exposure to sunlight, particularly during periods of hot weather and high humidity.

Hot water showers and baths are sources of heat that can result in elevations in core body temperature. In multiple sclerosis (MS) patients, this can further interfere with electrical signals from already damaged nerves and lead to a temporary exacerbation of symptoms or the appearance of new ones. However, if patients can tolerate the heat well, hot tubs may be a good approach to ease MS symptoms such as muscle stiffness and nerve pain. It is generally recommended patients ask their healthcare team if hot tubs are safe in their situation.

The abnormal immune response that drives multiple sclerosis (MS) can cause damage to brain regions involved in regulating body temperature. Indeed, several studies have shown people with MS have an impaired sweating response, manifesting as delayed or reduced sweating in response to heat, which makes it difficult for them to maintain normal temperatures. This also may contribute to heat sensitivity in MS.

While many people with multiple sclerosis (MS) have a reduced sweating response, there are several reports of patients who experience severe bouts of hot flashes and night sweats. This may be associated with MS-related damage in the autonomic nervous system, which helps control involuntary bodily processes like sweating. It also can be a side effect of certain MS treatments.

Multiple Sclerosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

Related Articles



Envelope icon

Subscribe to our newsletter

Get regular updates to your inbox.