I don't have a study, but my friends who have been having to wear the masks everyday are getting horrible acne and even staph infections. One even got a fungal lung infection. It's not so much the lack of oxygen, it's constantly breathing in hot/humid air containing your own bacteria for hours on end. Yes, your bodies own bacteria can give you an infection.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/
From 2015. Use of cloth masks showed higher rate of influenza like illness (ILI) than control group.
(https://www.rcreader.com/commentary/masks-dont-work-covid-a-review-of-science-relevant-to-covide-19-social-policy)
Check out this twitter feed: https://twitter.com/AlexBerenson/status/1283053298065510401?s=20
https://aapsonline.org/mask-facts/
I don't have a study, but my friends who have been having to wear the masks everyday are getting horrible acne and even staph infections. One even got a fungal lung infection. It's not so much the lack of oxygen, it's constantly breathing in hot/humid air containing your own bacteria for hours on end. Yes, your bodies own bacteria can give you an infection.