The effects of temperature on MS

Jump to:

• Why do my MS symptoms get worse when it’s hot?
• What are the long-term effects of heat on MS?
• Can warm weather affect MS?
• Exercise and temperature
• How can I keep cool with MS?
• Why do my MS symptoms get worse when it’s cold?
• Keeping warm with MS in cold weather

MS and heat sensitivity

When you get too hot, you may notice changes to how you feel - like difficulties with balance, weakness, or fatigue, or changes to your vision or sensation. These are all common effects from the heat. But it's an individual thing. Some people find it harder to concentrate, or might notice it affects their coordination. This heat sensitivity is sometimes called 'Uhthoff's phenomenon'. 

Why do my MS symptoms get worse when it’s hot?

There might be a few reasons MS symptoms get worse when it’s hot: 

• a rise in your body's core temperature
• warmth on your skin 

Core body temperature

Nerves don’t work so well when they’re too warm. So when the body’s core temperature rises, messages find it harder to pass along the nerves in the brain and spinal cord. 

And MS can damage nerve fibres or their protective outer layer (myelin). This makes them much more sensitive to the heat. 

In the brain and spinal cord, messages pass along nerve fibres to control all the different parts of the body. So when the body's too warm this makes symptoms worse, until the nerve fibres cool down again.

Warmth on the skin

Sometimes symptoms feel worse even when the core body temperature hasn’t gone up. There are theories about why this might be, including: 

• MS might sometimes affect nerves outside the brain and spinal cord - 'peripheral nerves' which have myelin around them. Just like affected nerves in the brain and spinal cord, they might not work so well in the heat.
• There might be a psychological effect. If you know it makes your symptoms worse, noticing that warmth on your skin could have a real effect on the symptoms you feel.

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What are the long-term effects of heat on MS?

No long-term harm is thought to come from the body getting warm. MS symptoms usually return to their previous levels as your body cools down. Often that's in less than an hour. Some people do feel more fatigued than usual for several hours, or even a few days, but recovery can be much quicker.

It's important to check that there isn't another reason for symptoms changing, like an infection. Speak to your GP or MS nurse if you're concerned.

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Can warm weather affect MS?

Warm weather can affect MS symptoms for some people. And we've got tips for keeping cool. But it's not the only thing that brings on heat-related symptoms. Other causes of Uhthoff’s phenomenon can include

• exercise
• sunbathing
• hot baths
• using a hair dryer
• fever caused by an infection 

Changes in hormone levels might cause changes in body temperature. For example, during the menstrual cycle or menopause. Just before, and during a period, the core body temperature rises a little. This can sometimes make MS symptoms feel worse.

Read more about periods and MS

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Exercise and temperature

Exercise is good for us. It can help with overall health, as well as with some of the effects and symptoms of MS, like: 

• fatigue
• balance and walking
• mood

If the heat affects you, you might find you need to adjust the kind of exercise you do. For example, doing shorter exercise sessions, or focussing a bit more on strength and balance instead of endurance. Your GP, MS nurse, physiotherapist or occupational therapist might all be able to give useful advice. 

And there are ways to stay cooler before and during activity which can help too. 

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How can I keep cool with MS?

There are lots of ways people find to stay cool when they exercise or in hot weather. You might find your own that work better for you. You might find others ideas in our online forum.

Keep cool while exercising

If you’re exercising, here are just a few ideas for keeping cool: 

• Cooling before exercise with a cooling vest or other special clothing which uses ice or fluid to cool the body. These can be hard to wear while you exercise, but can help if you use them before you start
• Cold drinks
• Sucking on ice
• Taking cool baths before or after (start with warm or slightly warm water and increase the coldness to avoid a shockingly cold experience)
• Staying in an air conditioned space – for example, an accessible gym

Keep cool on holiday and in warm weather

When it's really warm, it helps to:

• avoid hot environments like kitchens, very sunny rooms or direct sunlight
• search out air-conditioned hotels, cafés and restaurants
• avoid long car trips unless you have effective air conditioning
• keep curtains or blinds closed in the day to stop the heat building up

What you wear can keep you cooler

Everyday clothes and special garments could help:

• wear light-coloured, loose-fitting clothing
• keep your head covered if you're in the sun
• try clothing with 'wicking' properties. They draw moisture away from the skin and, through evaporation, help keep your temperature stable
• use cooling vests with ice packs or ‘active’ ones that get plugged in to stay cool. Cooling vests are often most practical for 'pre-cooling' before activity, or if you’re not moving around a lot

MS sometimes changes the way a person experiences hot and cold on the skin. So it's important that, for example, ice packs aren't left directly on the skin.

Use cooling accessories and techniques

• keep a hand-held mini-fan close by
• moisten clothing using a water spray
• dip sports sweat bands in cold water and put them on both wrists
• try chilling pillows which you can put your feet on during the day and slip inside your pillowcase at night for all-day cooling
• on long car journeys, you could keep spare cool collars and ties in cool boxes (and electric plug-in cooling clothes are great for re-cooling ones that have started to warm up)

Hydrate

• increase your fluid intake (try cold water or drinks with crushed ice)

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What is the MS hot shower sign?

Sometimes the effect of heat on MS is called the ‘hot shower sign’, the ‘hot bath test’ or ‘Uhthoff's phenomenon’. 

The hot shower or bath refer to old ways to diagnose MS, looking for the effect of heat on someone’s symptoms. Uhthoff's phenomenon is named after Dr Wilhelm Uhthoff who first described the effect, in 1890. Dr Uhthoff was a German eye specialist who noticed that people with optic neuritis had worse symptoms when they were exercising. 

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Night sweats and MS

If you have night sweats and you’ve got MS, there could be another cause for this symptom. Research hasn’t noticed a link between sweating a lot and MS. In fact, some people with MS might sweat less than other people. 

So if it’s not that hot but you’re waking up with your clothes or bedding wet with sweat, let your GP know. They can help you find out what’s causing it and ways to manage it. For example, night sweats can be caused by anxiety or the menopause. 

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MS and feeling cold

Some people with MS find the cold is a problem. In one survey, a third of people with MS were sensitive to both hot and cold. If the cold affects you, you might notice sensory symptoms or mobility gets worse until you warm up again. Or perhaps your muscles feel stiffer than usual, or more prone to spasms. 

If you can find a comfortable temperature, these effects should fade away.

Why do my MS symptoms get worse when it’s cold?

There could be a few reasons why MS symptoms can get worse when you’re cold. 

One is because muscles and joints don’t work so well in the cold. That’s true for people with or without MS. But if you already have some muscle stiffness, you might really notice the impact of the cold in that way. 

Another reason is likely the same as the way heat affects things. The nerves in your brain and spinal cord need to be a comfortable temperature to work at their best – not too hot or too cold. If the core body temperature changes a few degrees either way the nerves can’t pass their messages so well.  

One part of the brain might be particularly important. The hypothalamus plays a big part in controlling body temperature. If MS affects this part of the brain, the body might not be so good at keeping a comfortable core temperature. 

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Keeping warm with MS in cold weather

Our bodies can generate heat from moving around, so it can be harder to stay warm if your mobility is affected. Of course, warm clothes can help, as might heat pads and hand warmers.

But MS sometimes changes the way a person feels hot and cold on the skin. So it's important that a heat pad or hot water bottle is not too hot and is not left directly on the skin. This can cause blisters and burns.

If you're layering up, you might need to experiment. For example, some people find tight clothes painful. They can trigger muscle spasms. On the other hand, some people with tremor find tight clothes helpful. You'll find what’s best for you, whether that’s tight-fitting thermal wear or layering looser clothes. Both can help keep you warm. 

We can lose heat from anywhere on our body, so hats, thick socks and lined boots are all good for warmth.

Frequent hot meals and hot drinks can help warm the body. Storing a hot drink in a flask can help avoid repeated trips to the kettle.

You might also be eligible for financial and practical help with heating and insulating your home.

Find out more about dressing for warmth from Living Made Easy 

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