Read This Before Wearing Your Face Mask In The Rain

Masks are widely recognized to help prevent the spread of COVID-19, by reducing transmission of the virus when people cough, talk, sneeze, shout, or project your voice (via CDC). Masks have been widely used across the United States and much of the world in the form of simple cotton face masks or disposable hospital surgical masks. As the seasons change from mild, drier summers in the Northern hemisphere to colder and wetter weather, a new concern has been raised about how these conditions will affect masks and disease prevention. 

After a recent rainy spell in Britain, Tim Spector, who is a professor of genetic epidemiology at King's College London, noted to The Times: "It would now be useful if clear advice were issued to the public ... Masks need to be changed regularly and this is particularly important to understand in damp and wet weather." That's because a damp mask simply isn't effective at preventing disease transmission.

Here's why you need to change your mask if it gets wet

In the same Times story, Professor Karol Sikora, a former head of the WHO cancer program explains, "Moisture makes masks porous, and because of this, all types of mask are essentially vulnerable in damp weather." And disposable surgical masks might be the most affected. Professor Paul Hunter studies Medicine at University of East Anglia and describes disposable masks as being "essentially made out of paper" (via HuffPost). When dry, these masks have a barrier between the paper layers that helps block respiratory droplets, but as it gets wet the whole works begins to disintegrate. 

Even N95 masks get low marks in wet weather, leading health professionals to widely recommend that you change any mask for safety after it gets wet. And the WHO concurs, suggesting people "replace masks as soon as they become damp with a new clean, dry mask" (via Yahoo! Sports) There is also a risk of "potential self-contamination that can occur if medical masks are not changed when wet, soiled or damaged." Bottom line: If your mask becomes damp, stay safe by reaching for a new one.