Many people with multiple sclerosis are sensitive to heat and changes in body temperature. Even a quarter- or half-degree change in core body temperature can temporarily trigger MS symptoms. Environments others might not think twice about — a humid backyard, stuffy room, or hot shower — can make MS symptoms worse. This condition is called Uhthoff’s phenomenon.
The effects of heat on MS symptom flare-ups are so well established that before the invention of MRI, doctors used to give a hot bath test to people they believed had MS. If the person’s neurological symptoms suddenly flared in hot water, the physician would presume their diagnosis was correct.
Thankfully, tests like those are unnecessary today. With some planning and preparation, people with MS can use strategies to avoid the complications of heat sensitivity.
In people with MS, the body’s immune system attacks the central nervous system, causing inflammation and stripping the nerves of their myelin (protective coating). This process, known as demyelination, leaves the nerves vulnerable and reduces their ability to transmit electrical signals to the brain.
Research indicates that when a person with MS experiences an uptick in core temperature, neural conduction (the passing of messages along nerve fibers) slows down. In some cases, it may be blocked entirely. This can cause a worsening of MS symptoms. The severity of the flare-up depends on the extent of a person’s demyelination and how much their core temperature has heated up.
MS can negatively affect a person’s ability to maintain a healthy body temperature. If a person develops a lesion in an area of the brain that regulates core temperature or cooling responses (such as sweating or circulation), they may not be able to adjust to a warmer environment.
Heat intolerance, or heightened sensitivity to heat, is one of the most common symptoms of MS. This condition affects between 60 percent and 80 percent of people with MS. These individuals may experience a pseudo-exacerbation (temporary symptom flare) if their core body temperature rises. Warm environments can trigger a temporary worsening of MS symptoms, as can exercise and fevers caused by illness or infection.
Watch MS expert Dr. Aaron Boster discuss how temperature changes can affect MS symptoms.
Members of MyMSTeam often discuss heat sensitivity and temperature changes. “If I am hot, I am weak,” one member said. “Any slight warmth over 70 F, and I reel. Heat sucks,” shared another.
“Don’t have a problem being cold,” one member said. “It’s the heat that shows me MS is still in charge."
Heat can affect energy levels and mobility. One member described hot days as, “Like I am trying to walk through Jell-O and everything hurts.” Another said, “I get fatigue really bad, and brain fog.”
“I also get too hot and have an almost heatstroke-like reaction, and I get dizzy and nauseous,” another member said.
Many say the heat limits their productivity. “I am constantly overheating, it makes it difficult to do anything” one member shared. Another said, “Hot weather, I seem to tire faster, so I take a little more time doing things.”
One member said a trip to a hot vacation destination put them in the hospital. “Heat and humidity are my enemies!! I went to a family reunion, and the heat and humidity made my MS flare up so bad. I had a horrible MS hug, felt like I couldn’t breathe, and lost consciousness.”
The MS symptoms most commonly associated with heat intolerance include:
One MyMSTeam member shared that they experience worsened muscle symptoms in the heat. During heat waves, they wrote, “The good old legs decide to fight me big time.”
MS symptoms caused by heat sensitivity are usually temporary. They generally go away once the body cools down.
It’s important to be aware that relapsing symptoms or flares caused by heat can also create secondary health risks. As one team of researchers explained, heat sensitivity in people with MS is strongly correlated with fatigue. When compounded with cognitive problems and muscle weakness, fatigue and heat sensitivity have been reported as predictors of accidental falls.
When you’re in the middle of a heat-prompted MS flare-up, you can take a few immediate actions to cool yourself down. You might try:
If you opt for a cooling shower or bath, be sure not to shock your system with water that is too cold. Start with lukewarm water, then slowly lower the temperature.
You can reduce your future risk of pseudo-exacerbations by creating a schedule and home environment that takes temperature into consideration. Ask your doctor or neurologist what they advise for protecting yourself from the heat.
If you want to work out, do so in a cool environment. Avoid hot or stuffy rooms. If you plan any outdoor activity, try to do it during the cooler early morning hours or in the evening.
Don’t overexert yourself, and take regular breaks. As one MyMSTeam member shared, “My physical therapist noticed one day that I don’t rest between activities. I just push on through. We had a serious talk about giving myself permission to rest.”
Be sure to have water on hand while exercising. Consider setting aside 30 minutes after your workout for a cooling bath or shower. This can help you safely lower your core temperature and keep cool.
If you live in a hot or humid climate, you may want to consider investing in air conditioning or fans. These will help you regulate the air temperature of your home and limit your chance of experiencing environmental heat triggers.
“I bought a personal and portable AC unit for my household,” one MyMSTeam member shared. “The really nice thing about it is that I can take it anywhere with me, so that I can have a way to beat getting heat stroke/overheated.”
If you find lightweight garments aren’t enough to help you cope with the heat, you may consider specialized cooling clothes. These garments are often specifically made for people who have MS. They contain a gel-like substance that can be chilled before use and provide cooling effects for several hours or days. These cooling products come in a variety of forms, including neck wraps, bandanas, hats, and wristbands.
If you need more cooling support than gel-lined clothing can provide, you may want to try a cooling vest. These vests resemble waistcoats and feature battery-powered cooling packs that keep your torso cool. Because cooling vests are often designed for athletes, they usually stay comfortable even during vigorous physical activity. Research indicates that people with MS who use cooling vests may be able to walk farther and longer without fatigue than their peers.
“I have a cooling vest and have fans on me all the time,” one MyMSTeam member said. Another shared a creative way to achieve a similar effect: “I was having a very hard time getting a cooling vest. So I went to the secondhand store and got a fishing vest, and packed it with ice packs. LOL! My vest lives in the freezer.”
Everyone with MS experiences symptoms differently, and what works for one person may not be suitable for another. It can be a trial-and-error process to find what works best for you.
Living with multiple sclerosis can be complicated, but you don’t need to face the challenge alone. MyMSTeam is the social platform designed to connect, support, and empower people who have MS.
On MyMSTeam, more than 195,000 members come together to share stories of life with MS. You can ask questions, provide insights, and even just make conversation with people who truly understand what it’s like to live with MS.
Does heat affect your MS symptoms? Do you have a tip to share on staying cool? Start the conversation by leaving a comment below or making a post on MyMSTeam.