CHICAGO (CBS)– Rumors about whether masks cause hypercapnia are circulating social media.

Hypercapnia occurs when you breathe in too much carbon dioxide. University of Chicago’s Chief Epidemiologist says there’s no need to worry.

“Masks are meant to filter air, not to hold all the air in, That’s the difference between a plastic bag and a mask,” Dr. Emily Landon said.

If you’re having trouble breathing, doctor Landon recommends washing your mask as dust and debris may be clogging it.

She also says if your mask hasn’t been washed, this can cause skin irritation and acne to develop.