The second people realise they've caught a cold, the first reaction is typically: Get this thing out of my body so I can get along with my life, please. In the quest to feel better, some people contemplate just taking a hot yoga class or sitting in a sauna to "sweat it out." In a way, it seems like sweating would flush out a cold and exorcise any "toxins." But that's not really how it works.
Contrary to popular belief, sweat doesn't really have any detoxifying superpowers. When your core body temperature rises, your brain tells your sweat glands to do their thing. Then, a mixture of water, ammonia, urea, salts, and sugar (aka sweat) evaporates on your skin to cool you down. There may be minuscule amounts of toxins that leave your body through sweat — but that won't necessarily improve your health, particularly if you have a cold.
When you have a virus, it rapidly spreads and circulates all throughout your body, explains Janejira Chaiyasit, DNP, assistant professor at Columbia University School of Nursing and a nurse practitioner at its faculty practice, ColumbiaDoctors Primary Care Nurse Practitioner Group. Usually, a virus ends up infiltrating all different kinds of cells, which means it's difficult for a virus to totally escape your system without medication and lots of "work" from your body, she says. "It is unlikely that you can get rid of a virus completely by raising your body temperature and sweating," she says.
Some people assume that sweating will get rid of a cold because it's like putting your body into a fever, but it's not that simple, either. When you have a fever, your body is actively trying to fight and kill off an illness by increasing circulation and raising your body's core temperature, Chaiyasit says. "It is your body’s defence mechanism, and results as your immune system is preparing to develop the necessary cells to attack," she says. Usually, when your fever "breaks," it means your body temperature returns to normal, and you may feel sweaty.
But simply raising and lowering your core body temperature by exercising or sitting in a hot room won't accomplish the same outcome as a fever, Chaiyasit says. Also, the life of a virus depends on several factors besides just temperature, like your body's pH, the type of host cell the virus latches onto, and other physical barriers. "[Temperature] is definitely an important aspect, but does not determine a virus' viability solely," Chaiyasit says. In other words: You can't just zap a virus to death.
All this considered, sometimes exercise can do you some good when you have a cold. "Exercise definitely helps improve blood flow, which can help bring immune cells to the site of an infection to actively fight off a virus," Chaiyasit says. But if you over-exert yourself, it can lead to dehydration and shunt blood flow. In general, if you're sick, it's a good idea rest so your body can focus on the infection, she says.