It's pointless to wear a surgical mask over a fabric mask - the other way around is most effective, study finds

• Double masking can improve your protection against the coronavirus.
• Layering a cloth mask over a surgical mask can improve the fit while maintaining good filtration.
• However, wearing a surgical mask over a cloth mask does not provide any added benefit.

Sometimes, wearing two masks is better than one. Dr. Anthony Fauci has endorsed wearing two masks for a firm and comfortable fit, and the Centers for Disease Control and Prevention have found double masking can improve protection by about 50%.

However, double masking may not be necessary if you already have a well-fitted mask, found a recent study published as a research letter in JAMA Internal Medicine.

Researchers at the University of North Carolina at Chapel Hill tested several mask combinations on volunteers, from a single cloth mask to doubled-up surgical masks. They found that wearing a full-coverage mask, such as a bandanna or gaiter, over a surgical mask provided the best filtration.

"[This] leads us to understand that double masking is most effective because of the improved fit that it offers, not because of the additional layers," lead author Emily Sickbert-Bennett wrote in an email to Insider.

Layering a cloth mask over a surgical mask also improved the fit and filtration, the study found. However, the same combination with the surgical mask on top provided no additional benefit compared to wearing a single surgical mask alone.

Surgical masks filter particles well, but their fit can be improved

Most surgical masks are built from nonwoven polypropylene layers, the same material used to make top-tier N95 respirators. Some are even fitted with an electrostatic barrier meant to trap infectious particles, airborne virus expert Linsey Marr previously told Insider.

But surgical masks may fall short on fit compared to cloth options. Layering a cloth mask on top combines the superior filtration of a surgical mask with improved fit.

If double masking sounds uncomfortable, there are other ways to make a surgical mask fit better. In a CDC study of double masking, knotting the ends of a surgical mask and tucking the fabric so that it wrapped more snugly around the wearer's face worked nearly as well as doubling up.

Other scientists have suggested using a mask brace to make a single surgical mask adhere better to the face.

Double masking is very effective - if everyone's doing it

Both the CDC study and the recent Chapel Hill research found that mask-wearing works best when both people interacting are wearing well-fitted masks.

"The best form of double masking is when you and the person you are interacting with both have a mask on," Sickbert-Bennett said.

This universal masking approach could achieve a 95% reduction in infectious particles, no matter which well-fitted option people choose, the CDC study concluded.