Everything you need to know about MS and hot weather

Summer has finally arrived, and with it comes a list of things you wished you knew before a sunburn blasted your chest.

Heat sensitivity is, of course, an uncomfortable sensation many people struggle with and is therefore not a symptom solely attributed to MS. The difference from other illnesses lies in how heat affects the central nervous system.

Uhthoff’s phenomenon is when changes in body temperature make a person’s existing MS symptoms worse; even a rise of 0.25°C to 0.5°C in the core body temperature is enough to cause upsetting symptoms in those living with MS.

Because of nerve damage in MS, symptoms will depend on the severity and the part of the nervous system that is damaged. Excessive heat sensitivity in MS causes a temporary worsening of existing symptoms and, more worryingly, can also cause new symptoms.

As such, physical exercise or prolonged exposure to a warm environment should be monitored. Although no nerve damage will occur because of an increase in temperature, you may still feel like you just entered a relapse. A flare-up of existing symptoms caused by another medical event is therefore called a ‘pseudo-exacerbation’ or ‘pseudo-relapse’.

Studies have shown that heat sensitivity is a key clinical factor in MS.

The science behind MS symptoms in heat, why it happens and risk factors to know before it’s too late.

What?

▪️Temporary exacerbation of existing MS symptoms and new disturbing symptoms when exposed to elevated temperatures,

▪️‘Pseudo-exacerbation’ of the symptoms, as an increase in temperature as such does not cause any nerve damage,

▪️Disturbance or block in the normal physiological nerve conduction mechanisms. Demyelination not only causes slowing of nerve impulse conduction along the affected nerve fibres but is also linked to a phenomenon called Frequency Dependent Conduction Block,

▪️Premature fatigue when people with MS are exposed to even a slight increase in temperature,

▪️Energy down to a bare minimum,

▪️Recharging very hard to achieve,

▪️Intense limb weakness,

▪️Visual problems,

▪️Neuropathic pain due to damage caused to the thalamus and the spinothalamic-cortical pathways leading to thermo-regulatory dysfunction,

▪️Worsening numbness,

▪️Pins and needles,

▪️Dizziness,

▪️Cognitive dysfunctions like memory problems,

▪️Judgment difficulties,

▪️Concentration difficulties,

▪️Language comprehension,

▪️Slurred speech,

▪️ Nausea and a feeling of fainting about to happen.

Who?

60 to 80% of people with MS have excessive heat sensitivity issues.

Why?

A slight increase in core body temperature (0.25°C to 0.5°C) occurs due to nerve damage in MS patients.

Nerve transmission requires more energy in the heat, and even more with demyelination.

Causes?

▪️Physical exercise,

▪️Warmer environment,

▪️Cooking in front of a hot oven and over a hot stove,

▪️Eating or drinking hot food and/or fluids,

▪️Warm indoor and other heat-inducing surroundings,

▪️Sunbathing or being outdoors in hot weather,

▪️Bathing in hot water,

▪️Strong emotional responses or experiences,

▪️Fever,

▪️Use of a hairdryer,

▪️Hormonal changes in women,

▪️Hot flashes during menopause.

How to handle?

▪️Avoid working outside during the warmest hours of the day (11am to 4pm),

▪️Seek out shade and/or carry an umbrella wherever you go,

▪️Take lukewarm showers instead of cold ones. Taking cold showers only helps you stay cool for a short time, as your body’s core temperature will warm up due to reduced heat loss from the body without skin blood flow. Some minutes later, we feel hot again. But a warm sensation on the skin will lead to increased blood flow to the skin, increasing heat loss from the body,

▪️Keep your head and neck area cool with a wet, cool towel from the freezer,

▪️Stay well-hydrated,

▪️Use hand-held fans like fan-topped spray bottles to cool down your face,

▪️Use a desk fan at work,

▪️Add short breaks to your schedule to avoid full depletion of your energy levels,

▪️Keep your freezer stocked with small ice packs, cold water bottles, neck wraps,

▪️Wear cooling vests or bras with cooling pads in them,

▪️Wear loose-fitting, breathable white clothes in layers,

▪️Drink ice water with lemon, or cold iced tea, avoiding anything sugary,

▪️My Cooling Towel, a $15 to $20 scarf-shaped piece of fabric that, once dampened, displays unique cooling properties. It can be draped around your neck, wrapped around your head or wrists, or laid across your legs to offer maximum cooling on the hottest parts of your body. Amazon sells different kinds of Cooling Towels and other ways to keep your body temperature down.

When to seek medical intervention?

Medical intervention isn’t always necessary for symptoms of Uhthoff’s. If you’ve experienced it before, you’ll know what to expect. But it’s easy to confuse heat-related symptoms with other medical emergencies.

When heat-related MS symptoms require medical attention:

▪️You’ve never experienced severe heat-related symptoms of MS before,

▪️You’re uncertain that your symptoms are Uhthoff’s or MS-related,

▪️You have accompanying symptoms unrelated to MS,

▪️Your symptoms don’t improve after you’ve cooled down.

Is emigrating to a climate that suits you better the answer?

While heat and humidity can trigger a wide range of MS-related symptoms, so can cold weather. High humidity or cold temperatures can trigger involuntary muscle spasms or stiffness, called spasticity.

If you have heat- or cold-related symptoms of MS, it’s best to avoid exposure to any extreme temperature. If you’re thinking of relocating for health reasons, it’s a good idea to spend some time in a different climate first to see if it makes a difference.

(In my case, living in Ireland in a more temperate climate helps my heat sensitivity, as summer temperatures in Belgium are testing for me)

Important!

If you or a loved one has MS, have a plan in place for staying cool, but also be ready for the unexpected. For example, a car breakdown could leave you stranded with no way to cool down. A battery-powered spray bottle fan filled with water and tossed in the trunk might be all you need to keep Uhthoff’s Syndrome at bay.

History of Uhthoff’s Phenomenon/Sign

Among the various symptoms of MS, Wilhelm Uhthoff, in 1890, described the peculiar phenomenon of ‘temporary worsening of symptoms with exercise’ in patients with optic neuritis. Optic neuritis is a condition affecting the eyes. It is a common problem for many people with MS.

Uhthoff noticed that visual symptoms were aggravated when people with MS performed exercise. While he attributed exercise to be the etiology of this problem, it was later realized that any action or condition that increases the core body temperature can worsen the symptoms in MS patients, and therefore not just those related to vision. This is called Uhthoff’s phenomenon or Uhthoff’s sign.

MS causes nerve damage, and nerves relay information to and from the brain. With 50+ different and possible symptoms associated with MS, it’s hard to pin down which is the most annoying. While you will not have every single one on the list, some will have a larger impact on your daily life than others.

More info

Heat sensitivity with MS, National Multiple Sclerosis Society

Temperature sensitivity, Multiple Sclerosis Trust

While you’re here, why not check out these pages?

Sensory MS symptoms: the hair that isn’t there

About Vikings, vitamin D and searing multiple sclerosis

Body image and MS: how many selfies do you have?

Why a rise in your body temperature can trigger MS symptoms