How to help your body cope in hot weather
Skin flushes, heart pounds and we breathe faster as body aims to cool itself
As people across Ontario, Quebec and major cities in the U.S. swelter under a June heat wave, medical experts are urging them to take precautions in the potentially deadly weather.
Much of Eastern Canada is dealing with extreme heat and humidity.
Matt Grinter, a meteorologist at the Weather Network based in Oakville, Ont., said Toronto's Pearson airport broke the humidex record for June on Sunday, making it feel as hot as 46.3 C. The stretch of high temperatures is expected to last three days, Grinter said.
In summer 2021 in British Columbia, 619 deaths were attributed to a heat event, according to a B.C. coroner's report. Many of the people who died had chronic health conditions, including schizophrenia, depression, substance use disorders, diabetes, heart disease and respiratory disease.
Edward Xie, an emergency physician at Toronto's University Health Network, said public health units, doctors and nurses focus on 26 C, because the B.C. event showed the highest risk of death was related to indoor temperatures above that temperature throughout the heat event.
Here's what Xie and other experts say happens to the body in the heat and what they recommend to stay safe.
Heat-related symptoms to watch for
"We have warm skin, we might look flushed, we may feel that our heart is pounding faster and we're breathing more to get that blood moving," Xie said, listing symptoms of heat exhaustion.
Our bodies are very effective at normal human body temperature of around 37 C.
But when the weather is hot, blood vessels expand to carry more blood to try to get rid of the extra heat faster through the skin, Xie said.
Symptoms of heat exhaustion can also include dizziness, headaches, fast breathing and thirst and can affect anyone.
When that happens, the person needs to cool down within 30 minutes.
"The most important thing is to get somewhere cool as quickly as possible," said Greg Wells, a senior scientist at Toronto's Hospital for Sick Children and an exercise physiologist.
Heat stroke, when the body's core temperature goes above 40.6 C — is one of the more serious risks. It's a medical emergency that can lead to long-term organ damage and death. Symptoms include rapid breathing, confusion or seizures, and nausea.
How to prevent overheating
To try to stay cool.
Some ways to do that, according to Wells and Health Canada, include:
- Get out of the sun and head indoors, preferably where there is air conditioning.
- Wear light-coloured clothing.
- Put on a hat.
- Keep the sun off your body by covering up.
- Consider exercising in the morning or evening instead of during the day.
If you're already overheating, they recommend:
- If there's no A/C, Wells said to use what's available, such as towels with cool water on them to help remove some of the heat from your body.
- Stay hydrated to ensure you have enough fluids to sweat and keep the heat coming off the body.
- Take cool showers or baths until you feel refreshed.
The importance of sweat and hydration
While it may smell unpleasant, sweating is your body's friend.
That's because it helps heat dissipate. The higher the temperature gets, the more sweating becomes the main way the body cools, Xie said.
But when it is really humid, that cooling function gets harder because the sweat doesn't evaporate off your skin as quickly and is less effective at pulling the heat from your body, said Wells.
Babies, pregnant people and those age 65 or older aren't able to produce sweat as effectively.
Xie said some medical conditions also impair the body's ability to sweat, and some medications have a dehydrating effect, which can be problem in the heat.
"There are many heart medications that allow people to get rid of water in their body," Xie said. "Well, you can imagine that during a heat wave, they need that extra water to not get dehydrated."
Those medications include, but are not limited to, antihistamines, anti-inflammatories, heart medications, anti-nausea drugs, thyroid medications, ADHD medications and antidepressants.
Modifying movements
People taking diuretics to eliminate excess fluid in their heart, legs or lungs or on medications to control high blood pressure could be at risk of passing out in extreme heat, said Peter Wu, an internal medicine physician at the University Health Network and head of the pharmacology and toxicology division at the University of Toronto Faculty of Medicine.
"It's controlling your blood pressure, and then now you go out into the heat, which further causes your blood vessels to dilate and drop your pressure, and you sweat, and you lose fluids, and you drop your pressure further," Wu said.
However, it's important not to stop or modify the dose of such medications without talking to your doctor first, he said.
Beyond staying cool and hydrated, moderating your movements can also help mitigate some of the combined effects of heat and medications, Wu said.
"Don't rush your transitions, like from lying down to sitting to standing," he said. "Just giving your body a moment to settle and let the blood flow regulate that way."
Wells, from Toronto's SickKids, says among the best ways to prevent some of the negative effects of heat is to listen to your body.
"The most important thing is to use yourself as a laboratory," he said. "Pay attention to how you're feeling; pay attention to your heart rate; pay attention to how much you're sweating; stay hydrated."
Sun sensitivity
Some medications, such as certain antibiotics and acne medicines, make you more sensitive to sunlight and mean you can get sunburned more easily while taking them.
In those cases, it's all the more important to use and reapply sunscreen and wear long sleeves, Wu said.
Some medications can also be susceptible to high heat; insulin or epinephrine injections, for example. But generally speaking, as long as you're following storage instructions and not leaving drugs in a hot car for hours on end, there shouldn't be any significant effects on efficacy, Wu said.
With files from CBC's Christine Birak, Melanie Glanz and Reuters
