evidence: Research has found that wearing a mask (with at least two layers of fabric) is one of the most effective methods Americans can take to slow the spread of the coronavirus. Yet health myths about masks flood social media — people worry that wearing masks will lower oxygen levels or cause carbon dioxide poisoning. Others fear they’ll develop bacterial infections from moist, sweaty masks or weaken their immune system’s ability to fight off colds. [...] As for whether masks might compromise one’s immune system, Schaffner said "that’s malarkey." [...] "I can pretty much guarantee to you that wearing a mask intermittently throughout the day or even all day long is not going to weaken your immune system," he said.