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MS and fever

Fevers can be particularly difficult for people with multiple sclerosis (PwMS). Although regular flu symptoms can be bad enough, fevers can also make existing or old MS symptoms worse.

Fevers can be particularly difficult for people with multiple sclerosis (PwMS). Although regular flu symptoms can be bad enough, fevers can also make existing or old MS symptoms worse.

Symptoms of fever

Although it is normal for body temperature to vary during the day between 36°C and 37.5°C, it is not normal for temperature to rise above 38°C (low grade fever) or even 39°C (high grade), and is usually an indication of infection.

When a fever coincides with a cold or flu, this may simply be a sign of the body’s own defence mechanism for dealing with the infection. Our white blood cells tell the brain to increase body temperature to make the virus or bacterium uncomfortable and aid the immune system to fight the infection. This is usually effective, but the resulting heat stress can have unpredictable results for PwMS.

For PwMS, symptoms can get worse without an increase in lesions – this is all known as a ‘pseudo-exacerbation’ which can mean both a return of old symptoms and a worsening of existing ones.

Although these symptoms should return to a normal baseline level as the body cools (Uhthoff’s phenomenon), as can be seen during exercise, it can make the already very unpleasant flu even more debilitating for PwMS, as it will often worsen fatigue, cognitive problems, balance and visual disturbance.

What to do if you have a fever

Normally, the best strategy is to ride out the fever by keeping it as close to 37°C as possible. You could also try some of  the following:

  • Keep your temperature comfortable and consistent. Avoid switching between extremes, such as going straight from a warm room to a cold room.
  • Take plenty of clear fluids.
  • Monitor your temperature regularly. This will make taking appropriate action easier.
  • Take as much bed rest and sleep as you need.
  • If you start to shiver, warm yourself gradually. Don’t be encouraged by a bout of shivering into turning on an electric blanket, adding blankets to the pile, or cuddling a hot water bottle or two. That may send your temperature soaring as shivering is one of the body’s mechanisms of increasing your core temperature.
  • If your temperature starts to spike, cool yourself gradually. Take a lukewarm shower, have someone massage you with rubbing alcohol, or use a cool, damp cloth to bathe your face, neck and shoulders.
  • Dress warmly. Wear pyjamas and bed socks in bed, and a dressing gown and slippers when you have to be up and about.
  • In bed, keep layers of blankets on the bed. Peel them back or flip them back onto you as necessary. Use the lightest amount you can. It’s a balancing act. You don’t want to add fuel to the fever and send it soaring, but you don’t want to get too cold either.
  • Paracetamol can help to reduce a fever if cooling yourself naturally isn’t working. The maximum dosage in 24 hours is 4g, and even small accidental overdoses can be very dangerous.
  • You may also talk to your GP or chemist about ibuprofen or aspirin as an alternative to paracetamol (but be wary if you are asthmatic or have stomach problems)

Whilst flu is very unpleasant it is not usually harmful and is self-limiting within 5-7 days.

Seek medical attention if:

  • Your temperature spikes above 40°C,
  • You’ve had a high grade fever for more than three days, without signs of it letting up,
  • A fever being accompanied by:

Severe diarrhoea,


Severe headache,

Neck stiffness,

Being bothered by bright light,


Problems staying awake,

Or any other signs of serious illness

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