Heat Sensitivity and MS: Getting Through an Australian Summer

Heat sensitivity and MS: getting through an Australian summer

Multiple sclerosis is a disease of the temperate world. The latitude gradient is one of the most reproducible findings in its epidemiology, and in Australia it is stark: Tasmania runs at 190.1 cases per 100,000 against the Northern Territory’s 37.2.

Which produces a particular Australian problem. The people most affected by MS live in a country where summer routinely exceeds 35°C, and heat does something to MS that it does to almost no other condition.

A rise in core body temperature of as little as 0.2 to 0.5°C is enough to worsen MS symptoms. That is less than the variation produced by a brisk walk, a hot shower, a warm room, or a mild fever. MS Australia’s Keeping Cool survey — 2,385 people with MS, a 76% response rate — estimated that around 90% of Australians with MS are heat sensitive, and found that 84% of respondents experienced extreme fatigue as a result, with 62% reporting other symptoms worsening.

This guide covers the mechanism, what to do about it, and — the part almost nobody knows — the funding and concessions available in Australia, including an Administrative Appeals Tribunal decision that established air conditioning as a fundable disability support rather than a household expense.

Uhthoff’s phenomenon: the mechanism

In 1890 a German ophthalmologist, Wilhelm Uhthoff, noticed that some of his patients’ vision blurred during exercise and cleared again when they cooled down. The effect carries his name, and the term is now used broadly for any MS symptom that worsens with heat.

The mechanism is straightforward once you know what myelin does. Myelin insulates nerve fibres and lets electrical signals travel fast and cleanly. Where MS has stripped it away, conduction along that fibre is already marginal — signals get through, but slowly and unreliably.

Nerve conduction is temperature-sensitive. Raising the temperature of a partially demyelinated fibre slows conduction further, and past a threshold the signal fails to propagate at all. So a pathway that was just barely working at 36.8°C stops working at 37.2°C. That is the whole phenomenon: a conduction block produced by a fraction of a degree, in nerves that had no margin left.

Some people also have lesions in the hypothalamic regions that regulate body temperature, which produces genuine temperature dysregulation on top of the conduction problem.

Pseudoexacerbation: it is not a relapse

This distinction matters enormously and is routinely missed, including by emergency departments.

Heat-related worsening is a pseudoexacerbation. It is temporary, it resolves on cooling, it causes no new nerve damage, and it does not indicate new disease activity. It is a functional unmasking of damage that already exists, not the creation of more.

A relapse, by contrast, develops over hours to days, lasts more than 24 hours, is not explained by temperature or infection, and reflects new inflammation.

Why the distinction is practical: a person who presents in February unable to walk, after a 38°C day, may well not need steroids. They need to cool down. Treating pseudoexacerbations as relapses means unnecessary intravenous methylprednisolone, which has real side effects, and it muddies the relapse history that treatment decisions and NDIS applications rely on.

The other side of that coin: do not assume all summer deterioration is heat. Infection — especially urinary tract infection — raises core temperature and is extremely common in MS. A fever from a UTI produces exactly the same picture. Sudden worsening in a person with MS should prompt a urine culture, every time. See bladder, bowel and continence in MS.

What heat actually does to people’s lives

The Keeping Cool data is worth reading in full because it moves heat sensitivity from a medical curiosity to a disability with measurable consequences.

Among 2,385 Australian respondents with MS:

• About 84% reported extreme fatigue as the main problem caused by heat
• About 62% reported other MS symptoms worsening
• Roughly 45 to 49% said heat stopped them socialising, doing household tasks, or working effectively
• About 19% needed more medication because of heat
• About 9% needed to see a doctor or health professional
• About 3% had been hospitalised

Nearly half of Australians with MS cannot work effectively, keep house or go out during hot weather. In much of this country that is several months of the year.

The symptoms heat most commonly produces are blurred or double vision, fatigue, weakness, poor coordination, slurred speech and slowed thinking. Worth noting: some people with MS are sensitive to cold instead of, or as well as, heat — cold can worsen spasticity and stiffness particularly.

The cost, which is the part that gets ignored

The same survey measured air conditioner use, and the numbers are extraordinary.

About 82% of respondents used an air conditioner to keep cool. Nationally they averaged 1,557 hours of use between September and April. In Victoria, respondents averaged 1,508 hours against 107 hours for the average Victorian household — roughly 14 times as much.

They switched the air conditioner on at an average of 29.2°C, which is not an indulgent threshold.

Estimated annual cooling costs ran $520 to $693 nationally against $117 to $156 for an average household, and reached $823 to $1,097 in Queensland.

Set that against income. In the wider study, about 52% of Australians with MS had household incomes below $26,000 a year. And the survey found that concession-eligible and non-eligible respondents used air conditioners at similar rates — because, as the report put it, keeping cool is a very high priority for people with MS irrespective of their capacity to pay. People were running the air conditioner whether or not they could afford it.

Also worth knowing: about 74% had air conditioners four or more years old, which are materially less efficient, and about two-thirds could only afford to cool one or two rooms.

Practical cooling: what works

In rough order of cost-effectiveness.

Behavioural and scheduling

Move the day. Demanding activity into the cool hours — early morning especially. Check the forecast and plan around it, including humidity, which independently worsens the effect.

Pre-cool. Cooling before activity extends the amount of activity possible. A cold shower or ten minutes in air conditioning before going out buys capacity.

Lower the shower temperature. Hot showers are one of the most common unrecognised triggers, and in the morning they can cost the whole day. Lukewarm or cool is a free intervention.

Cold fluids, constantly. Internal cooling genuinely works, and hydration matters independently. Caffeine and alcohol are both counterproductive — diuretic, and in MS the bladder is often already a problem.

Know the escape route. Where the air conditioning is at the shopping centre, the library, the pool.

Equipment

Cooling vests. The best-evidenced piece of equipment. Two main kinds: phase-change vests, which use inserts that freeze at a set temperature and give steady cooling for a few hours, and evaporative vests, which are soaked in water and work well in dry heat and poorly in humidity. Phase-change is usually the better choice in most of Australia. They are not cheap — several hundred dollars — and they are legitimately assistive technology. Some state MS organisations and charitable grant programs assist with them, including heat-management grants; ask your state MS organisation.

Cooling accessories. Neck wraps, wrist bands, caps, and cooling towels. Cheap, and cooling the neck, wrists and scalp is disproportionately effective because of blood flow close to the surface.

Fans, including misting fans. Evaporative cooling works well in dry heat.

Air conditioning. The main event, and the subject of the funding section below.

Aquatic exercise. Water at around 28°C or below lets people with MS exercise at intensities they cannot manage on land, because the water carries the heat away. This is why hydrotherapy pools, typically heated to 33–34°C, are often the wrong setting for MS — a standard lap pool is frequently better. Worth checking the temperature before committing to a program.

The house

The Keeping Cool respondents had already done more of this than the general population: about 70% had roof insulation, 40% external window coverings, 27% wall insulation.

The highest-value items are external shading — awnings, blinds outside the glass, shade cloth, deciduous planting — because stopping heat before it enters the glass beats removing it afterwards. Then ceiling insulation, then sealing draughts, then creating one properly cooled retreat room rather than trying to cool the whole house.

Funding and concessions in Australia

This is the section to read, because most people with MS are paying for things they do not have to.

Medical cooling electricity concessions

Every mainland state and territory has a concession or rebate for people whose medical condition requires cooling, and MS qualifies. The names vary — medical cooling concession, medical heating and cooling concession, life support and medically required heating or cooling rebate — and they are administered by state energy or community services departments, usually requiring a form signed by a GP or specialist.

They are not generous relative to the costs above, but they are real money, they recur annually, and a large number of eligible Australians with MS have never applied. Your state MS organisation will know the current name and process. This is worth half an hour.

The NDIS: air conditioning as a disability support

Here is the part that surprises people, and there is case law.

In McKenzie and NDIA [2019] AATA 3275, a man with MS living in far north Queensland sought NDIS funding to replace his 18-year-old, undersized air conditioning system. His MS symptoms worsened as his core temperature rose.

The NDIA refused, arguing that there was insufficient evidence about how he managed temperature in community settings, that many Queensland homes have air conditioning, and that it was an everyday household item the family had always had and should pay for themselves.

The Tribunal rejected all of that and approved the funding. The reasoning is worth knowing because it applies well beyond this one case:

Social participation can happen at home. Mr McKenzie had not worked since 2013. Following Pavilupillai, the Tribunal held that his social participation occurred substantially within his domestic life at home, and that air conditioning would assist with those activities. This matters for anyone whose participation is largely home-based.

It is not a day-to-day living cost. The Tribunal described replacing the system as a “one-off or at most several times in a lifetime cost,” and held that widespread ownership in the region did not convert it into an ordinary household expense. Following Milburn, it accepted that air conditioning is discretionary spending for a person without disability but found that for Mr McKenzie it related directly to his need for support.

Whether the family could pay is not the question. Following McGarrigle, the Tribunal held that Parliament did not intend decision-makers to ask whether family or community could contribute.

The principle, in a sentence: whether something is a disability support or a day-to-day expense depends on the person and their disability, not on how common the item is.

What that means for an application. Cooling — air conditioning, a cooling vest, portable units, external shading, ceiling fans — is a legitimate assistive technology and home modification question. The way to put it is with an occupational therapist’s assessment linking the cooling specifically to function: what the person can and cannot do at given temperatures, how often those temperatures occur where they live, what the cooling enables, and why cheaper alternatives will not achieve the same outcome. Value for money was one of the elements the Tribunal considered, and it is answerable with evidence.

It is also, on MS Australia’s own account, badly underclaimed. And slow: the 2026 MS Australia survey recorded a respondent waiting about two years for air conditioning approval while their condition worsened. Start early and document thoroughly.

Other routes

State MS organisations run heat-management and equipment grant programs — MS Plus in Victoria, NSW, the ACT and Tasmania, MSWA in Western Australia, MS Queensland, MS Society of SA & NT.

Home energy efficiency programs in several states fund insulation and retrofits for low-income households, and MS respondents already use these at above-average rates.

Energy hardship and payment plans. Every retailer must offer them. A medical cooling concession and a hardship arrangement can run together.

Heatwaves: the plan to have before summer

Heatwaves kill more Australians than any other natural hazard, and people with MS are among the groups at elevated risk — both from the direct physiological effect and because mobility and cognitive symptoms worsen precisely when quick decisions are needed. Add a blackout, which takes out the air conditioning, and the situation becomes genuinely dangerous.

A written plan, prepared in spring:

• Where you will go if the house becomes unmanageable or the power fails — a relative’s house, a library, a shopping centre, a cooling centre
• How you will get there if you cannot drive and it is 40°C
• Who checks on you, on what days, by what method — and what happens if you do not answer
• A charged phone and a battery pack, because a blackout takes the landline and the NBN with it
• Frozen inserts for the cooling vest already in the freezer, and ice packs
• Medication storage, since some MS medications need refrigeration — know what yours requires and have an esky plan
• Your support provider’s heatwave protocol, in writing. Ask for it. A provider supporting people with MS should have one, and should know to reschedule rather than cancel, to bring the day forward, and to check in on hot days

If you receive supports, ask that the plan be attached to your support plan so that any worker on shift can follow it.

What support workers should know

Brief and concrete.

Heat worsening is real and physiological, not a mood or a reluctance. Someone who walked in unaided this morning and cannot stand at 3pm on a 36°C day is not inconsistent; they are hot.

Cool first, escalate second. If someone deteriorates in heat, get them cool — shade, air conditioning, cold drink, cool cloth on neck and wrists, cooling vest — and reassess. Most pseudoexacerbations resolve within an hour or two of cooling.

But take fever seriously. If there is any suggestion of infection, or the person does not improve on cooling, that is a medical review and a urine culture, not more fans.

Schedule around the heat. Move personal care earlier, keep the shower cool, do community access in the morning, and say so to the coordinator if the roster fights the weather.

Do not warm the bathroom. A heated bathroom and a hot shower is a common and entirely avoidable way to start somebody’s day badly.

Check the car. A car that has been in the sun is 60°C inside. Air conditioning on before the person gets in, not after.

Record it. “Unable to transfer independently from 2pm, ambient 34°C, resolved after 45 minutes in air conditioning” is exactly the evidence that supports an air conditioning or cooling vest application later.