Summer is around the corner, and here in Boston we’ve already had a few warm days. When that happens, it feels like everybody in my neighborhood rushes out the door to soak in the sunshine. The CDC now recommends—and many states mandate—that people wear cloth masks in public places where social distancing isn’t possible. As a result, the parks and trails are now packed with people wearing a rainbow of colorful face coverings.
But it doesn’t take long for things to get ugly: Your sweat and warm breath, coupled with the heat and humidity, creates a dank, swampy microclimate under the mask. This makes it difficult for cool air to reach the lungs, which can result in shortness of breath. In Japan, which recently recorded its highest temperature this year, doctors recommend that people take extra precautions (such as drinking more water and increasing rest) when wearing a mask in the heat to avoid heat stroke and exhaustion.
The moisture trapped within masks isn’t just uncomfortable, some researchers say it could actually be harmful. One 2015 study found that moisture retention in masks can create the conditions for bacteria and viruses to thrive. This is even worse if you wear the same mask multiple times before washing it. When damp, masks become less effective at preventing the spread of viruses, which is why some states, such as Pennsylvania, explicitly say masks should not be worn when wet from spit or mucus.
In other words, it’s important to be vigilant about keeping your mask clean and dry, for comfort as well as safety. Here’s a four-part strategy for wearing masks in the sweltering months ahead.
Pick a breathable fabric
For starters, think about the right fabric for your mask. A lightweight, breathable material like cotton or linen will allow for more airflow. Some researchers point out that if a mask isn’t breathable, it forces airflow out through the sides, which actually defeats the purpose of catching droplets from the wearer’s nose and mouth.
If you’re looking for a mask that will keep you cool and comfortable in the summer, cotton is a good bet. One study found that using a single layer of T-shirt fabric blocked out 40% of particles from leaving the mask, and two layers of T-shirt fabric blocked out 98% of droplets, while maintaining breathability.
But those numbers only apply to the droplets you’re breathing out, as nonmedical masks are designed to prevent the wearer from infecting others. Highly breathable materials actually let in a lot of particles, so these aren’t necessarily designed to keep the wearer from being infected. As my colleague recently reported, tightly woven materials with a higher thread count are more effective at filtering out particles, as is layering fabrics on top of one another. If you’re trying to protect yourself, wearing a mask made from high thread count cotton, plus two layers of chiffon or silk will perform almost as well as an N95 mask, provided that it has a close fit on the face.
Get your strap tension right
Straps on a mask can be hard to wear both comfortably and effectively. To start with, there’s a wide range of possible strap materials, including strips of cloth, ribbon, string, shoelaces, and elastic bands. The goal is to ensure that the straps keep the mask in place so there aren’t huge gaps, while allowing you to breathe comfortably. Dermatologists point out that elastic straps can irritate the skin behind the ears, especially when it’s hot outside. As a result, it might be better to use an adjustable strap that you either tie or tighten with a clasp, so you can get a better fit. It’s worth spending a few moments fixing your mask before you head out the door so you’re not tempted to keep touching the mask, and by extension your face, when you’re out.
Don’t stay out too long
Some doctors recommend that you limit the amount of time you’re outside wearing a mask, if you’re not a medical professional or frontline worker. That’s because the average cloth mask doesn’t do a good job protecting the wearer. A mask shouldn’t lull you into a false sense of security: Spending time around a lot of other people in the midst of a pandemic may increase your risk of getting infected. So try to avoid crowded areas whenever possible and plan your errands or outdoor excursions during less busy times. One study showed that when the temperature was more than 80 degrees Fahrenheit and there was high humidity, many people found masks intolerable. The natural impulse in that case is to take it off, which doesn’t just remove the protection, it means you’re touching your face, which can spread the virus.
Wash, wash, wash
It’s crucial to wash your mask every time you wear it to keep it clean and prevent bacteria from growing on it. The CDC says a washing machine is sufficient; a cleaning expert at the Good Housekeeping Institute Cleaning Lab says masks should be washed with hot water and dried on high heat. And keep in mind that more delicate handmade masks might fall apart in the machine, so they should be washed by hand in hot, soapy water. As a final step, ironing masks on the cotton setting will kill any remaining germs.
From personal experience, it can be very easy to forget to wash your mask. After coming home from a sweaty walk, I can’t wait to take off my mask and hop in the shower. It’s only when I’m ready to head out again that I realize my mask hasn’t been washed. Now, when my family returns from a walk, we immediately run a load of laundry full of our masks and the clothes we wore out. In that case, it’s a good idea to have a couple masks, so even if you forget to wash it, it’s easy to grab another one.