Dr. Michael Osterholm, a coronavirus adviser to President Biden, appeared to question Dr. Anthony Fauci’s seeming embrace of double masking, or wearing two masks at once, suggesting during an appearance on MSNBC Thursday that the practice “may actually be counterproductive.”

“There’s a lot of talk that double masking is going to become an official [Centers for Disease Control and Prevention (CDC)] recommendation,” MSNBC’s Chuck Todd said, asking Osterholm where he falls on the subject.

Unlike Fauci, who in recent interviews did not dismiss the idea of double masking, Osterholm warned it could be “counterproductive.”

“In terms of using the face cloth coverings, doubling them, actually, we need to be very careful about that,” he told Todd. “That may actually be counterproductive, not helpful.”

“We know, and I’m not an aerobiologist, but we know that, in fact, they may actually impede the movement of air in and out and causing it to actually escape in the big crevices between the cloth and your face. That’s a bigger problem, not a lesser problem than one,” he continued, warning that “too thick of a cloth” will prevent air from moving efficiently, causing the feeling of suffocation.

“And the air then moves in and out of the cracks. So that’s why we have to be very careful about people making recommendations right now about double masking and so forth without really having the data to support that,” Osterholm added.

His rebuttal comes days after Fauci, chief medical adviser for President Biden on the novel coronavirus, appeared to support the prospect of double masking, telling TODAY’s Savannah Guthrie it “just makes common sense that it would likely be more effective.”

“You know, it likely does because, I mean, this is a physical covering to prevent droplets and virus to get in,” he said when asked if the practice makes a difference.

“So if you have a physical covering with one layer, you put another layer on, it just makes common sense that it would likely be more effective, and that’s the reason why you see people either double masking or doing a version of an N95,” he added:

During a Tuesday appearance on America’s Newsroom, Fauci again failed to rule out double masking, even for those who have been vaccinated.

Fauci’s current position on masks and double masking stands in sharp contrast to the opinion he held in March 2020, suggesting masks provided more psychological relief than practical.

“Right now, people should not be walking, there’s no reason to be walking around with a mask,” Fauci said at the time.

“When you’re in the middle of an outbreak, wearing a mask might make people feel a little bit better, and it might even block a droplet, but it’s not providing the perfect protection that people think that it is,” he continued, mentioning the “unintended consequences.”

“People keep fiddling with the mask and they keep touching their face,” he added:

The debate over double masking has been rising in recent days, particularly as virus variants continue to spread.

“Wear your mask is becoming wear your masks,” the Washington Post reported on Thursday.

“The discovery of highly transmissible coronavirus variants in the United States has public health experts urging Americans to upgrade the simple cloth masks that have become a staple shield during the pandemic,” the outlet continued, adding that the change could be “as simple as slapping a second mask over the one you already wear, or better yet, donning a fabric mask on top of a surgical mask.”