Temperature sensitivity and MS

Temperature sensitivity describes the worsening of symptoms that occurs in some people with multiple sclerosis (MS) in response to either an increase or decrease in their core body or skin temperature. These effects are temporary and should reverse when the body temperature returns to normal.

On this page, we look at what temperature sensitivity is, the different types of temperature sensitivity that can be experienced in MS and why it happens.

Temperature sensitivity is very common in multiple sclerosis (MS). As many as 8 in 10 people with MS report their symptoms getting worse in response to a change in temperature.

The effect that heat and cold can have on MS symptoms has been recognised for over 100 years. The effects of heat were used to help diagnose MS in the past.

The worsening of symptoms associated with temperature sensitivity is not usually due to new damage. It is a temporary response to a change in your core body or skin temperature triggered by an external factor. 

These factors can include:

• the weather
• exercise
• a fever
• stress.

Even very small temperature changes can have a negative impact on symptoms. The worsening is usually in symptoms you have experienced before rather than new issues.

Once your temperature returns to normal, the symptoms should settle back down. If they have not resolved after 24 hours, it is worth contacting your GP or MS team.

Temperature sensitivity in MS can happen for several reasons.

Damage to the myelin of nerve cells (demyelination) in MS disrupts the transmission of nerve messages. Signals may be slowed or even completely blocked. Increases in heat or cold can further impact the transmission of nerve impulses. An increase (or decrease) of as little as 0.5°C can have an effect.

This is not usually a sign of new nerve damage. Rather, it is the central nervous system finding it more difficult to transmit signals efficiently.

MS lesions may occur in areas of the brain that regulate body temperature. The region known as the hypothalamus acts as the body’s thermostat to keep the body at about 37°C. If it is affected, normal responses such as sweating or shivering, which help the body to cool down or stay warm in extremes of temperature, may not work as they should.

There are three types of temperature sensitivity in MS. Most people find they are affected by heat. Some people report their MS symptoms getting worse in response to cold. Whilst others are sensitive to both heat and cold. This is sometimes referred to as combined or mixed temperature sensitivity.

Heat sensitivity, also known as Uhthoff’s phenomenon, is the most common type of temperature sensitivity experienced by people with MS. It describes the temporary worsening of MS symptoms in response to an increase in temperature. Warm, humid weather is one of the main triggers. Fatigue and weakness can be especially worsened by heat.

Read more about heat sensitivity, including common triggers, the symptoms that are affected and how to cope with increases in temperature.

Cold sensitivity describes the temporary worsening of MS symptoms in response to a decrease in temperature. It is much less common than heat sensitivity in MS. It is usually triggered by cold weather or sitting near a draught. Stiffness can especially be worsened in the cold.

Read more about cold sensitivity, including common triggers, the symptoms that are affected and how to cope with decreases in temperature.

Combined sensitivity describes the temporary worsening of MS symptoms in response to an increase or decrease in temperature. Here, symptoms flare up when your core or skin temperature goes up or down by a small amount.

The good news is that there are lots of things you can try yourself to help with the effects of temperature sensitivity. The most useful approach will depend on the type of temperature sensitivity you experience. 

The first step will be to identify any triggers that you’re especially sensitive to. For example, you may find hot and humid climates are an issue, but you can cope with sunnier climates where the heat is drier.

Read more about ways to manage heat sensitivity.

Read more about ways to manage cold sensitivity.
 

Sometimes what appears to be temperature sensitivity can actually be a sign of something else.

If you are heat sensitive and experience any of the following, it is worth checking in with your GP or MS team if any temperature-related symptoms:

• are new issues or significantly worse
• last longer than they usually do
• don’t improve after cooling
• are accompanied by signs of infection or fever – infections can mimic or worsen symptoms and can trigger MS relapses.

These might be signs of infection, a relapse or pseudorelapse. Your GP or MS team can help determine what is going on.

You should check with your GP or MS team if you experience cold sensitivity and:

• pain such as numbness or tingling that doesn’t resolve 
• if stiffness, spasticity or spasms become significantly worse or persistent
• if symptoms don’t improve after you get warm.

If you can’t move your legs easily, or spend a lot of time sitting, you may find that the skin becomes blotchy or discoloured (mottled) in your lower legs and feet. This is because it is harder for the muscles to pump oxygen-depleted blood back up to the heart if you have limited mobility. As a result, the skin can have a bluish hue in white skin, or a purplish or grey hue in black or brown skin. But it is possible to also have the circulation condition Raynaud’s (NHS.UK) which causes similar discolouration of the skin. 

Feeling cold more than usual can also be a sign of an underactive thyroid (NHS.UK). 

Both of these conditions can overlap with MS, so if you’re at all concerned it is worth getting checked by your GP or MS team. 

As both temperature sensitivity and MS relapses can cause symptoms to worsen, you may be concerned about the reason for any changes you’re experiencing.

It is more likely to be temperature sensitivity if you can answer yes to the following questions.

• Did the symptoms start after exposure to heat or cold?
• Have you had these symptoms before?
• Did the symptoms improve within a few hours once you cooled down or warmed up?

It is more likely to be a relapse if:

• you’ve not been exposed to something that usually triggers your temperature sensitivity
• you’re experiencing new or significantly worse symptoms
• symptoms last for more than 24 hours with no improvement after cooling down or warming up
• symptoms continue to worsen over the following days
• you’re not showing signs of an infection or fever.

If you’re at all concerned, contact your GP or MS team.