PHILADELPHIA - Summers are getting hotter, something we have seen multiple times in Europe recently. Heat waves are becoming more intense and more frequent, thanks to the climate crisis.
Your go-to cooling method might be to blast a fan in your face to help evaporate the sweat. However, a new study suggests that depending on where you live, fans might be doing more damage to your body than helping.
The study was published this week in the Annals of Internal Medicine, an academic medical journal published by the American College of Physicians.
It found the use of fans during hot, dry conditions worsened body temperature, heart rate, body sweat rate and thermal comfort. In contrast, fan use in hot, humid conditions improved all of these except body sweat rate. Blood pressure did not change in either heat wave condition.
Humidity is key
It all depends on the amount of humidity in the air. The small study included just 12 participants with no known medical conditions who were analyzed in the simulated different climates, hot and dry versus hot and humid. The participants were exposed to a fan for two hours.
Particularly, the researchers focused on the effects of fan use on thermal strain, cardiovascular strain, dehydration and thermal comfort.
The heat index is the "apparent temperature," and is an accurate measure of how hot it really feels when the relative humidity is added to the actual air temperature, according to the National Weather Service.
The study simulated a humid heat wave where the heat index was 56 degrees Celsius (133 Fahrenheit) and a dry heat wave where the heat index was 46 degrees Celsius (115 Fahrenheit).
Fans reduced core temperatures and cardiovascular strain and improved thermal comfort in humid conditions. Fans worsened these parameters in dry conditions despite the lower heat index value.
The U.S. Environmental Protection Agency says using a fan above 37.2 degrees Celsius "actually increases the heat stress the body must respond to." When the air temperature is higher than the temperature of your skin, the more fans accelerate dry heat transfer toward the body.
Fans increase sweat evaporation off of the body. Most body sweat should evaporate freely, and when humidity is low, sweat already evaporates faster than humid environments.
So, if you live in an arid climate, such as the desert southwest U.S., the Middle East, Australia, and western South America, you might consider ditching the fan, and going straight to air conditioning to cool down.
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