Etsy sellers have sold hundreds of thousands of cloth face masks in the past few days, the company says, and demand is likely to outstrip supply soon now that the Centers for Disease Control and Prevention (CDC) has shifted its guidance on wearing such masks in public.

“We hope that increasing the availability of fabric, non-medical grade face masks from Etsy sellers will allow more medical and surgical masks to reach the people who need them most: front-line health care workers,” Etsy CEO Josh Silverman said in a statement Friday.

But while Silverman encouraged sellers to consider making the masks, a set of guidelines for sellers stresses that making medical claims about the masks is against its rules, and, advises sellers not to use the words “coronavirus” or “COVID-19” on their individual listing pages.

“Don’t use this language anywhere in your listing, including in the title, description, tags or listing photos,” Etsy wrote in a post on its Sellers Handbook. “Listings with medical claims may be flagged by shoppers and removed from the site. Shops that repeatedly have items removed could be suspended.”

The CDC released new guidelines Friday recommending that people in the US wear homemade face coverings to help prevent the spread of the coronavirus. US Surgeon General Jerome Adams said during a press conference at the White House that the agency is advising people use “simple cloth coverings to help people who may have the virus and do not know it keep from transmitting to others.”

The most effective masks to filter out droplets in the air that may transmit the virus are the N95 respirators used by health care providers, which are in gravely short supply. The cloth masks may reduce the amount of particles spread by people wearing them but they’re not meant to replace the N95 masks. Some experts suggest that wearing a cloth mask is better than nothing. “If you put something in front of your face, it’s going to help more than not,” virologist Julian Tang told Wired.

And, even if you’re wearing a mask, the CDC still recommends practicing social distancing during the coronavirus pandemic, which means staying six feet apart from others in public.