Ms., hot weather, and tips to stay cool

For 60 to 80 percent of people with multiple sclerosis (MS), summer can be difficult. Heat waves and high humidity levels often temporarily worsen MS symptoms. These may include visual disturbances, weakness, and fatigue.

The negative effects of heat on people with MS is called Uhthoff’s phenomenon. While at first associated only with vision problems, research has expanded the understanding of Uhthoff’s phenomenon to include other neurological issues as well.

It's thought that nerve cells damaged by MS become further impaired by heat, and are less able to transmit electrical impulses. Here’s what to know about how heat affects people with MS and strategies for dealing with it.

What happens, and why?

MS is a nerve and nervous system condition that damages the protective sheath around your nerve cells, and that damage slows down nerve signals. This leads to symptoms such as:

• Vision problems
• Balance and coordination difficulty
• Tingling or numbness
• Muscle weakness
• Concentration and memory issues

Researchers believe that when a person’s core body temperature rises, the heat further slows down nerve signals, increasing symptoms. This can result in a flare-up of MS symptoms.

It’s not just the weather that can increase symptoms, either. Sunbathing, exercise, and even a fever can all make MS symptoms worse. These heat-induced symptoms are thought to be temporary and cause no long-term damage, however. Once a person cools down, the symptoms usually go away, often in under an hour.

How to keep cool

Before the next heat wave, consider taking these steps:

Be prepared. Be sure to check the weather forecast before you go outside so you can make sure you’re prepared during high temperatures.

Avoid the heat. Prevention is best, so limit outdoor activities when it's really hot (more than about 86 degrees Fahrenheit) or humid. In heat waves or periods of high humidity, it’s best to stay indoors and run the AC or fan. Alternatively, get your fresh air during cooler parts of the day, like early morning or evening.

It’s not just summertime temperatures that can worsen symptoms. You’ll also want to avoid other warm situations, such as very hot showers, saunas, hot tubs, and pools that are overwarm.

Opt for cool clothes. A 2019 systematic review published in the journal Multiple Sclerosis and Related Disorders found that preparing for exercise or rising temperatures beforehand can be helpful. They looked at the benefits of wearing both active and passive cooling garments.

Active cooling clothes have tubes that circulate cold liquid, and passive clothing has ice or gel packs in them. Examples of passive cooling garments include vests, neck wraps, or bandanas that incorporate cooling elements. Using these types of garments before and after exercise is linked to a lower core temperature and improvements in the ability to exercise.

Besides special cooling garments, there are general best practices for dressing for the heat. When you're out in the sun, wear a wide-brimmed hat and loose, breathable clothing in light colors.

Cool off. Wading or stretching your arms and legs in a shaded pool can be refreshing and offer other great health benefits. Just be sure the water temperature is under 85 degrees Fahrenheit. And when you can't get to the pool, jump in the shower for a cool rinse. A tepid water bath, with colder water gradually added over the course of a half hour, is also helpful. And if none of this is convenient or available, use a cool misting spray.

Stay hydrated. On warm days or when you’re exercising and getting your body temperature up, regularly reach for cold drinks or frozen treats like popsicles.

If you’re experiencing heat-related MS issues, it can also help to consult with your healthcare provider. They’ll help you come up with strategies that work for you.