If you’ve noticed your MS symptoms flaring up on hot days, during exercise, or even after a warm shower, you’re not alone. Heat sensitivity affects between 60% and 80% of people with MS², making Australian summers particularly challenging for many of us.

The good news is that heat-related symptom flare-ups are temporary and don’t cause permanent damage or disease progression. Even better, there are many practical, affordable strategies that can help you manage heat intolerance and enjoy life even during the warmer months. Whether you’re heading into your first Australian summer with MS or you’re looking for new ways to stay comfortable, this guide brings together the latest research and real-world strategies that work.

Let’s explore why heat affects MS symptoms, what you can do about it, and how to plan ahead for a more comfortable summer.

Key Takeaways

• Heat sensitivity (Uhthoff’s phenomenon) affects 60-80% of people with MS, causing temporary symptom worsening that reverses when you cool down
• Even small temperature increases of 0.5°C can trigger symptoms, but these don’t cause permanent nerve damage
• Simple, affordable strategies like staying hydrated, using fans with moisture, and timing activities for cooler parts of the day can make a significant difference
• Cooling vests and garments have been shown to improve walking capacity and functional mobility in research studies
• Pre-cooling before exercise or going out can help prevent temperature rises and reduce symptom flare-ups

What Is Heat Intolerance in MS?

Heat intolerance, also known as Uhthoff’s phenomenon, is a temporary worsening of MS symptoms when your body temperature rises³. This was first described in 1890 by German ophthalmologist Wilhelm Uhthoff, who noticed his patients’ vision worsened during exercise.

Any increase in body temperature can trigger symptoms, whether from hot weather, exercise, fever, or hot showers. The key thing to understand is that these symptom flare-ups aren’t true relapses. They’re temporary responses to heat that resolve once your body cools down¹.

Why Heat Matters: Understanding the Impact

How Common Is Heat Sensitivity?

Research shows that between 60% and 80% of people with MS experience heat sensitivity². For many Australians with MS, summer can feel like a season to endure rather than enjoy.

The Real-World Impact

Heat sensitivity doesn’t just cause discomfort, it can significantly affect your daily life. Fatigue is one of the most commonly worsened symptoms in heat, often limiting people’s ability to exercise and perform everyday tasks⁶, especially during Australian summers.

You might find yourself:

• Avoiding outdoor activities during warmer months
• Struggling with increased fatigue in air-conditioned spaces that aren’t quite cool enough
• Needing to reschedule appointments or social events on hot days
• Feeling anxious about attending outdoor events

The good news is that with the right strategies, many people with MS can continue to participate in activities they enjoy, even during summer.

How Heat Affects MS

Why Your Nerves Struggle with Heat

In MS, your immune system has damaged the protective coating (myelin) around nerve fibres in your brain and spinal cord. Think of myelin like the insulation around an electrical wire, it helps signals travel quickly and efficiently.

When myelin is damaged through demyelination, nerve signals find it harder to travel the length of the nerve¹. Heat makes this worse by further slowing down these already struggling nerve signals. Even small increases in core body temperature -as little as 0.5°C – can slow nerve conduction in people with MS².

Your Body’s Cooling System May Not Work as Well

Some people with MS may have lesions in brain areas that control body temperature, affecting their ability to initiate sweating or send blood to the skin to cool down⁹. This means your body might not respond to heat as efficiently as it once did, making it harder to maintain a comfortable temperature.

Research also suggests that people with MS may start sweating at a higher body temperature than people without MS⁹, which can contribute to overheating.

Practical Cooling Strategies for Australian Summers

1. Hydration: Your First Line of Defence

Staying properly hydrated is essential for managing heat sensitivity. Water helps regulate your body temperature and supports overall health.

Practical hydration tips:

• Keep a water bottle with you throughout the day
• Drink cold or cool water regularly, especially during hot weather²
• Add water-rich foods to your diet—cucumber, watermelon, oranges, and tomatoes all contribute to hydration
• Avoid excessive caffeine and alcohol, which can dehydrate you
• If your urine is clear or pale yellow, you’re well-hydrated; darker urine means you need more water

2. Pre-Cooling: Get Ahead of the Heat

Pre-cooling means cooling down before exercise or going out in hot weather to help prevent temperature rises⁷. This simple strategy can make a significant difference.

Pre-cooling methods:

• Immerse your lower body in cool water for 30 minutes before exercise—this can reduce core temperature by approximately 0.5°C⁷
• Take a cool (not cold) shower before heading out
• Have a cold drink 15-30 minutes before activities
• Apply cold, damp cloths to your neck, wrists, and face
• Store a cooling vest or neck wrap in the fridge and wear it before going out

3. Smart Use of Fans and Air Flow

Research has shown that using a fan can deliver a significant cooling effect, particularly when combined with dampening your skin². This is particularly helpful for Australians facing high electricity costs.

Making the most of fans:

• Dampen your skin with water while using a fan- this enhances the cooling effect through evaporation²
• Position fans to blow directly on you, not just circulate air
• Use battery-operated portable fans when out and about
• Consider a misting fan that sprays fine water droplets while circulating air
• Close curtains and blinds during the hottest part of the day, then use fans to circulate cooler air in the evening

4. Cooling Vests and Accessories: What Actually Works

Cooling vests can be helpful, but they’re not essential for everyone. A 2023 systematic review found that cooling garments effectively improved walking capacity, functional mobility, and reduced symptoms in people with MS⁵. Several types are available in Australia, each with different benefits.

Types of cooling products:

Ice/gel-based vests: Multiple Australian suppliers offer cooling vests with frozen or chilled inserts.

• Pros: Effective cooling, can last 2-4 hours
• Cons: Can be heavy (around 1.4kg), need freezer access
• Cost: $150-400 depending on the model

Phase-change material (PCM) vests: These vests use special materials that maintain a steady, moderate temperature (typically 15-21°C).

• Pros: Lightweight, discreet under clothing, provide gentle, consistent cooling
• Cons: More expensive ($300-600), shorter cooling duration (2-3 hours)
• Best for: Active use, wearing under work clothes

Evaporative cooling products: These use water evaporation to cool you down.

• Pros: Very affordable ($20-60), lightweight, easy to use
• Cons: Less effective in high humidity and temperatures over 30°C⁶
• Best for: Dry climates, backup cooling option

Budget-friendly alternatives:

• Damp scarves or bandanas around your neck
• Frozen water bottles wrapped in thin cloth
• Cooling towels that you soak in water
• Gel cooling packs designed for picnic coolers

5. Timing and Planning Your Activities

Work with the weather, not against it:

• Check the forecast and plan your week around cooler days
• Schedule outdoor activities for early morning or evening, avoiding peak heat between 10am and 3pm⁶
• Break activities into smaller chunks with cooling breaks between
• Plan indoor alternatives for extremely hot days
• Allow extra time for tasks—rushing increases heat production

Exercise safely:

• Exercise in cool, shaded environments and take frequent breaks²
• Consider switching to swimming or water-based exercise during summer
• Use air-conditioned gyms when available
• Keep an icy drink nearby during workouts
• Listen to your body and stop if you feel symptoms worsening

6. Home and Clothing Strategies

Cooling your environment:

• Close curtains and blinds during the day to keep heat out
• Use ceiling fans in reverse (counterclockwise) to push cool air down
• Consider evaporative coolers, which are more energy-efficient than air conditioning
• Keep bedroom windows open at night for cross-ventilation
• Place a frozen water bottle in front of a fan for DIY air conditioning

Clothes:

• Choose lightweight, loose-fitting clothes in natural fibres (cotton, linen)
• Light colours reflect heat better than dark colours
• Look for clothes with mesh panels or moisture-wicking properties
• Wear a broad-brimmed hat for sun protection when outdoors
• Remove unnecessary layers as soon as you’re indoors

What to Do When Symptoms Flare

Despite your best prevention efforts, you might still experience heat-related symptoms. Here’s what to do:

Immediate cooling actions:

• Move to a cooler environment immediately
• Take a cool shower, starting with lukewarm water and gradually making it cooler⁹
• Drink cold water or suck on ice chips
• Apply cold, damp cloths to your neck, wrists, armpits, and groin
• Sit in front of a fan or in air conditioning
• Rest until symptoms improve

When to seek help:

• If symptoms don’t improve within 24 hours of cooling down³
• If you experience new symptoms you haven’t had before
• If you’re unsure whether you’re experiencing heat sensitivity or a true relapse
• If heat-related symptoms are significantly affecting your quality of life

Contact your neurologist, MS nurse, or GP if you have concerns.⁹.

Frequently Asked Questions

Is heat sensitivity the same as a relapse? No. Heat sensitivity (Uhthoff’s phenomenon) causes temporary worsening of existing symptoms that resolves when you cool down, usually within minutes to hours. A true relapse involves new symptoms or significant worsening that lasts at least 24 hours and occurs in the absence of fever or infection³.

Will heat exposure cause permanent damage to my nerves? No. Research confirms that heat-induced symptoms are completely reversible and don’t cause permanent nerve damage or disease progression¹. Once your body temperature returns to normal, your symptoms should improve.

How long does it take for symptoms to improve after cooling down? Most people find their symptoms begin improving within minutes to an hour of cooling down. If symptoms persist beyond 24 hours, contact your healthcare team as this may indicate a true relapse rather than heat sensitivity³.

Are cooling vests worth the cost? Research shows cooling garments can significantly improve walking capacity and reduce fatigue in people with MS^5,8. However, they’re not essential for everyone. Start with simple, low-cost strategies first. If heat sensitivity significantly affects your daily life, a cooling vest might be a worthwhile investment.

Can I still exercise if I have heat sensitivity? Yes! Exercise remains beneficial for people with MS. The key is exercising smartly: choose cooler times of day, work out in air-conditioned spaces when possible, use pre-cooling strategies, take regular breaks, and stay well-hydrated⁷. Water-based exercise is often better tolerated.

Why do I feel worse in the heat even if I’m not doing anything strenuous? Even without exercise, hot weather or environments can raise your core body temperature. People with MS may also have impaired sweating responses, making it harder for the body to cool itself naturally⁹.

Is it safe to use saunas or hot tubs if I have MS? Most people with MS find that saunas, hot tubs, and hot baths worsen their symptoms temporarily. While they won’t cause permanent damage, they can be quite uncomfortable. It’s generally better to avoid these activities or use them very briefly, followed by immediate cooling⁶.

Summary and Final Thoughts

Heat intolerance is one of the most common experiences for Australians living with MS, but it doesn’t have to control your life or limit your summer. The most important things to remember are:

Heat-related symptoms are temporary and reversible. They don’t cause permanent damage, even though they can be uncomfortable and frustrating in the moment.

Simple strategies often work best. Before investing in expensive cooling equipment, try basic approaches like staying hydrated, using fans with damp skin, timing your activities for cooler parts of the day, and pre-cooling before going out.

Everyone’s experience is different. What works well for one person might not help another. Give yourself permission to experiment with different strategies until you find what works for your body, your budget, and your lifestyle.

This summer, you can take control of heat intolerance rather than letting it control you. With some planning, practical strategies, and patience with yourself, you can stay safe, comfortable, and engaged in the activities that matter to you—even on the hottest Australian days.

References

1. Frohman, T., Davis, S., Beh, S., et al. (2013). “Uhthoff’s phenomena in MS – clinical features and pathophysiology.” Nature Reviews Neurology, 9(9), pp. 535–540.
2. Davis, S.L., Wilson, T.E., White, A.T., & Frohman, E.M. (2010). “Thermoregulation in multiple sclerosis.” Journal of Applied Physiology, 109(5), pp. 1531-1537.
3. Panginikkod, S., Rayi, A., Rocha Cabrero, F., & Rukmangadachar, L.A. (2022). “Uhthoff Phenomenon.” In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing.
4. Opara, J., Brola, W., Wylegala, A., & Wylegala, E. (2016). “Uhthoff’s phenomenon 125 years later – what do we know today?” Journal of Medical Life, 9(1), pp. 101–105.
5. Stevens, C.J., Singh, G., Peterson, B., Vargas, N.T., & Périard, J.D. (2023). “The effect of cooling garments to improve physical function in people with multiple sclerosis: A systematic review and meta-analysis.” Multiple Sclerosis and Related Disorders, 78, 104912.
6. Christogianni, A., et al. (2022). “Heat and cold sensitivity in multiple sclerosis: A patient-centred perspective on triggers, symptoms, and thermal resilience practices.” Multiple Sclerosis and Related Disorders, 67, 104075.
7. Kaltsatou A, Flouris AD. Impact of pre-cooling therapy on the physical performance and functional capacity of multiple sclerosis patients: A systematic review. Mult Scler Relat Disord. 2019 Jan;27:419-423. doi: 10.1016/j.msard.2018.11.013. Epub 2018 Nov 13. PMID: 30544086.
8. Buoite Stella, A., Pasquin, F., Morrison, S.A., et al. (2020). “Effects of a cooling vest with sham condition on walking capacity in heat-sensitive people with Multiple Sclerosis.” European Journal of Applied Physiology, 120(11), pp. 2467-2476. https://doi.org/10.1007/s00421-020-04478-3
9. Davis, S.L., Jay, O., & Wilson, T.E. (2018). “Thermoregulatory dysfunction in multiple sclerosis.” In: Handbook of Clinical Neurology, Volume 157, pp. 701-714. https://doi.org/10.1016/B978-0-444-64074-1.00042-2
10. Sumowski, J.F. & Leavitt, V.M. (2014). “Body temperature is elevated and linked to fatigue in relapsing-remitting multiple sclerosis, even without heat exposure.” Archives of Physical Medicine and Rehabilitation, 95(7), pp. 1298-1302. https://doi.org/10.1016/j.apmr.2014.02.004