Heat Sensitivity and MS: Why "Beat the Heat" Isn't Enough Anymore

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Yesterday, the temperature reached 31°C (88°F) for the second day in a row. No humidex. Just 31.

After a week of gorgeous, gentle weather in the mid-20s, I'd been outside as much as I could—because I love it. Shade in the afternoon, a lovely patio supper with a breeze in the evening, a light meal. Nothing that should have knocked me over.

By the time we got home, I couldn't stand up.

Every movement felt like wading through wet cement. My hands went numb. I took my temperature: 37.9°C (100.2°F). I slept it off, and this morning I'm mostly back to myself, though my temperature is still a touch elevated and I'm choosing to enjoy today's sunshine from behind a window.

The most surprising thing to me?

It was "just" 31 degrees.

Recent temperatures in Europe have climbed higher than those in the Sierra Desert, and some Ontario heat waves haven't been far behind. Climate patterns are changing, and with them, so is the way our bodies experience summer. So yes, I was surprised.

I'm telling you this not for sympathy, but because I want you to notice something.

I did most things "right."

I stayed in the shade.

I ate lightly.

I wasn't working hard.

It didn't even feel that hot.

But after spending most of my days outdoors enjoying beautiful weather, that jump to 31°C—and simply being outside for long stretches—was enough. Heat still took me down.

That's the piece I want to talk about this year.

Our summers have quietly stopped being something we joke about with "beat the heat" slogans. They've become a genuine health hazard, and not just for people living with a chronic health condition.

This Kind of Heat Hits People With MS Hard

For those of us living with multiple sclerosis (MS), heat sensitivity is old news.

Here's the simple version of why.

Your hypothalamus acts as your body's thermostat. In MS, inflammation and lesions can interfere with the pathways that help regulate body temperature. The vagus nerve serves as an important messenger, carrying temperature information from your skin to that thermostat. When that communication becomes glitchy—and when the body's ability to sweat is also compromised—heat has nowhere to go.

It simply builds.

That's the essence of dysautonomia.

The autonomic nervous system—the part that's supposed to quietly regulate temperature, heart rate, blood pressure, digestion, and so many other essential functions—isn't doing its job in the background anymore. Instead of your body adapting automatically, you feel every degree because your system can't compensate the way it should.

For many people with MS, even a small rise in body temperature can temporarily worsen symptoms like fatigue, weakness, numbness, blurred vision, balance problems, or brain fog. Cooling down often brings improvement, but in the moment it can feel as though your body has simply shut off.

If you've experienced it, you know exactly what I mean.

But This Isn't Just an MS Story Anymore

Here's what I really want you to sit with.

The temperatures we're now experiencing are becoming enough to overwhelm perfectly healthy regulatory systems too.

You don't need MS.

You don't need dysautonomia.

You don't even need a chronic illness.

You simply need enough heat.

When your core temperature rises, your body shifts into survival mode. Blood is redirected toward the skin to release heat. Your heart works harder. Digestion slows. Your cells operate under increased metabolic stress.

If the heat continues day after day—and especially if nights stay warm enough that your body can't fully recover—that stress begins to accumulate.

Heat isn't simply uncomfortable.

It's inflammatory.

It's depleting.

It quietly drains fluid, minerals, energy, and the physiological reserves your body depends on for healing, repair, and everyday function.

For someone already living with chronic illness, that reserve may already be limited.

But increasingly, healthy people are finding their reserve isn't limitless either.

The Quiet Signs Your Body Is Falling Behind

Some warning signs are obvious.

Others are surprisingly easy to dismiss because they don't look like "heat illness."

Pay attention if you notice several of these together after spending time outdoors or during prolonged hot weather:

• Swelling in your feet or ankles ("sausage feet")

• Urinating less often than usual

• Fatigue that feels much heavier than ordinary tiredness

• Headache

• Brain fog or difficulty concentrating

• Hot, flushed cheeks or bright red ears

• Dizziness when standing

• Numbness or tingling in your hands or feet

• A racing or irregular-feeling heartbeat

• Feeling unusually irritable or short-tempered
  

These are often your body's early warning signals.

They're the little flags before the big ones.

Listen while your body is still whispering.

Don't wait until it's shouting.

Why Electrolytes Matter More Than Ever

I know.

Everyone tells you to "drink your electrolytes."

It can start to sound like another wellness catchphrase.

But there really is solid physiology behind it.

Electrolytes—particularly sodium, potassium, and magnesium—allow your cells to hold onto water properly. They're essential for healthy nerve transmission, muscle contraction, heart rhythm, and maintaining fluid balance throughout your body.

When you're sweating heavily, plain water replaces fluid, but not everything you've lost.

Without replacing those minerals, you can end up feeling exhausted, lightheaded, crampy, or mentally foggy, even if you're drinking plenty.

One of my favourite options is wonderfully simple:

• Water or coconut water

• A pinch of good-quality sea salt

• A squeeze of fresh citrus

• A touch of maple syrup
  

Simple.

Effective.

No fluorescent colours required.

What the Old Wisdom Already Knew

Long before air conditioning, people learned to work with summer instead of fighting against it.

The Spanish and many Latin American cultures are famous for the siesta, closing shops and retreating indoors during the hottest part of the day.

But they weren't alone.

Across desert communities and throughout much of the Middle East, daily life traditionally shifted toward early mornings and evenings, with midday reserved for shade and rest.

In parts of India and throughout the Caribbean, there has long been an unspoken rhythm of slowing down when the sun is highest and picking life back up as the day cools.

Somewhere along the way, many of us traded that wisdom for productivity.

Air conditioning made it seem possible.

But as summers become hotter and heat waves last longer, I think it's worth borrowing that ancient wisdom back.

Not as a luxury.

As a remarkably practical health strategy.

Natural Cooling Strategies That Actually Help

One of the gifts of naturopathic medicine is that it reminds us how powerful simple things can be.

When it comes to heat sensitivity, water is one of our greatest allies.

Naturopathic Hydrotherapy isn't complicated. At its heart, it's about helping your body release heat more efficiently. Often that's through evaporation, but sometimes it's simply through the direct cooling effect of water.

You don't need fancy equipment to benefit.

A cool foot bath.

A cool or tepid shower.

A damp face cloth across the back of your neck.

A misting bottle filled with water and a drop of peppermint essential oil.

Each of these helps your body shed heat when it can't do the job effectively on its own.

Sometimes the simplest therapies are the most effective.

Reading this brought back one of my favourite memories from the first half of our marriage, when Mike and I spent our summers boating.

He became very good at recognizing the tell-tale signs that I was overheating before I did.

If he noticed my face flushing or my energy suddenly disappearing, there wasn't much discussion.

He would simply scoop me up...

...and throw me overboard.

Not very glamorous.

Very effective.

The ultimate hydrotherapy.

Thankfully, most of us have gentler options available—but the principle is exactly the same.

Helping the body release heat before it reaches its tipping point can make all the difference.

Practical Ways to Protect Yourself During Extreme Heat

As our summers continue to change, managing heat has become less about comfort and more about prevention.

Here are a few simple strategies that can make a meaningful difference.

Protect the Middle of the Day

Treat late morning through mid-afternoon as your low-exertion window.

If you need to garden, walk, exercise, or tackle outdoor projects, choose the cooler hours of early morning or later evening whenever possible.

The world has followed this rhythm before.

There's wisdom in it.

Hydrate With Minerals—Not Just Water

Water matters.

Electrolytes matter too.

Especially if you've spent time outdoors, have been sweating, or are living with a condition that affects your autonomic nervous system.

Think of hydration as replacing both the water and the building blocks your body needs to use it well.

Use the Right Tools for the Job

Sometimes the simplest tools make the biggest difference.

A wide-brimmed sunhat.

Lightweight natural fabrics.

A handheld fan.

Cooling towels.

Cooling scarves.

Cooling vests for longer outings.

These aren't signs of weakness.

They're tools that help your body do a job it's struggling to do on its own.

Watch for the Quiet Signs

Heat doesn't always announce itself dramatically.

Sometimes it whispers.

Swollen feet.

A fuzzy head.

Needing to urinate less often.

Feeling unusually irritable.

Your body is often giving you early information long before you're in real trouble.

Pay attention.

Rest Without Guilt

This one might be the hardest.

We've been taught to equate rest with laziness.

I don't buy that.

Sometimes the healthiest thing you can do is close the curtains, put your feet up, and let your nervous system recover.

An afternoon indoors isn't wasted time.

It's an investment in tomorrow.

Living Beyond the Diagnosis Means Listening to Your Body

One of the greatest lessons living with MS has taught me is that my body is always communicating with me.

Sometimes I listen well.

Sometimes I don't.

But the message is always there.

Living beyond the diagnosis has never meant pushing through at all costs.

It's meant learning to pay closer attention.

Learning when to move.

Learning when to rest.

Learning that working with your body almost always gets you further than working against it.

This summer, I think that lesson applies to all of us.

Whether you're living with MS, another chronic illness, or you're perfectly healthy, our climate is changing in ways that ask us to rethink old habits.

We may need to slow down a little more.

Hydrate a little better.

Respect the hottest part of the day.

And remember that taking care of ourselves isn't something we earn after we've finished everything else.

It's how we stay well enough to keep living the life we love.

So this summer, stay cool.

Stay curious.

Pay attention to what your body is telling you.

And take good care of yourself out there.

Frequently Asked Questions

Why does heat make MS symptoms worse?

Heat can temporarily slow the transmission of nerve signals along pathways already affected by multiple sclerosis. Even a small increase in body temperature may make symptoms like fatigue, weakness, numbness, balance problems, or brain fog more noticeable until the body cools down.

Can healthy people become heat intolerant?

Absolutely. As heat waves become more frequent and temperatures remain elevated for longer periods, healthy people can also struggle with heat regulation—especially if they're dehydrated, overexerting themselves, or not recovering overnight.

What are the early signs of heat exhaustion?

Early warning signs often include unusual fatigue, dizziness, headache, brain fog, swollen feet or ankles, flushing, reduced urination, a racing heartbeat, and feeling unusually irritable. Recognizing these signs early allows you to cool down before symptoms become more serious.

Are electrolytes better than water in hot weather?

Water is essential, but when you're sweating heavily or spending extended time in the heat, your body also loses important minerals like sodium and potassium. Replacing both fluids and electrolytes helps maintain hydration and supports healthy nerve and muscle function.

Does hydrotherapy help with heat sensitivity?

For many people, yes. Cool or tepid showers, foot baths, cooling cloths, and other forms of hydrotherapy can help lower body temperature, reduce discomfort, and support the body's natural cooling mechanisms.