Heat sensitivity and MS: why symptoms flare in warm weather

The MS Trust's page on heat sensitivity describes it as a temporary worsening of symptoms in response to a rise in temperature. It says the extra symptoms are not usually caused by new MS damage, and that once body temperature returns to normal they should settle within a few hours. The symptoms it lists are the ones a person already knows: fatigue, blurred vision, numbness and tingling, weakness, poor balance, and trouble concentrating.

The same page lists what can set it off:

• warm weather, and humid weather most of all
• a room that is overheated or crowded, including a house with the heating turned up in winter
• warm baths and showers, saunas and steam rooms
• exercise, because it raises the body's core temperature
• stress or anxiety
• a fever or an infection
• hormonal changes around periods and the menopause

This matters for the family because the change can look alarming. Your relative may be fine at breakfast, and by three o'clock their legs are weak, their vision is blurred and they are too tired to talk. Knowing it is heat, and that it usually passes, makes a hot afternoon less frightening. MS care at home sets out how the rest of the illness shapes a week.

The MS Trust's page on temperature sensitivity says to contact the GP or MS team if heat symptoms are new or much worse, last longer than they usually do, do not improve after cooling, or come with signs of infection or a fever. Its page on relapses explains that a relapse means symptoms lasting at least 24 hours with no other explanation, such as an infection or heat. It also says the GP practice can test for a urine infection, which can make MS symptoms worse for a while, and UTIs and sudden confusion covers what to look for. If it does turn out to be a relapse, MS relapse cover at short notice explains how to get extra help at home quickly.

Drinking enough in the heat can worry someone whose bladder is already a problem, and the temptation is to drink less to avoid getting caught out. The MS Trust's page on bladder problems advises against cutting down. It gives at least 1.5 litres in 24 hours as the general guide, and explains that too little fluid makes urine more concentrated, which irritates the bladder and makes infection more likely. Caffeine, alcohol and fizzy drinks can irritate the bladder too. Bladder and bowel care with MS covers what a continence service can do. The NHS advice on the rooms, fans and drinks is on its page about coping in hot weather, and hot weather and heatwaves covers the wider advice for older people.

Fatigue is the first symptom on the MS Trust's list of those that heat makes worse, so a hot day needs more pacing than a cool one. MS fatigue and managed days explains how pacing works and why a rest planned before an effort helps more than one taken after it. On a hot day the same rule applies, with the rests moved into the hottest hours.

Poor balance is on the same list. If your relative's balance gets worse in the heat, keep walking in the hot hours to short, familiar routes inside the house. A perching stool in the kitchen, a shower seat, and a walking aid kept where it is needed all make the hot hours safer. Mobility aids and the home with MS covers what to ask for and who pays.

Travel and holidaysSection titled Travel%20and%20holidays

The MS Trust's guide to holidays and MS suggests choosing a time and a place with a climate that suits your relative. It also suggests keeping medication in hand luggage in its original packaging, with a copy of the prescription. If the room temperature is likely to be above 25 degrees, it suggests asking the travel company about a fridge for any medication that needs one. It also warns that standard travel insurance is unlikely to cover mobility aids. If a carer's help would make the trip possible, can you take a carer on holiday with you explains how that is arranged.

1. 1

   Plan the week around the forecast

   Before the hot spell

   When hot weather is coming, agree with your carer to move the shower, the shopping and any appointments into the mornings, and keep the afternoons free for rest.
2. 2

   Keep the cooling going

   Through the day

   Curtains closed before the sun comes round, the fan on, cold drinks refilled, a cooling scarf or vest on, and the windows opened again in the evening.
3. 3

   Notice what changes, and write it down

   Every visit

   What time the symptoms came on, what came before, and whether they eased once your relative cooled down. That note is what the MS nurse will ask for.
4. 4

   Know when to ring someone

   Agreed in advance

   Agree with the family who the carer calls, and when. New symptoms, symptoms that do not settle, a fever or signs of heat exhaustion all mean a phone call rather than waiting.

Hourly visits from carers on PrimeCarers cost £18 to £25 an hour with our fee included, against £28 to £35 an hour through an agency. An hour each morning through a week of hot weather is seven hours, which comes to £126 to £175 on PrimeCarers. If your relative with MS would like help on hot and tiring days, you can search for carers near you and compare their rates.

Carers on PrimeCarers are self-employed people you find, interview and book directly. We are an introductory service, not an agency or a care provider, so we do not provide or manage care. Before a carer appears, we check their identity and right to work, run an enhanced DBS check (or PVG in Scotland, Access NI in Northern Ireland) issued within the last 18 months, and interview them online. Every visit booked through PrimeCarers is insured, either by the carer's own policy or by cover we arrange where they do not hold one. We do not check qualifications, training or references. What a carer says about their MS experience is their own account on their profile, so ask them about it when you speak to them.