Researchers compared a mannequin with a mustache made from human hair and a mannequin without facial hair. They drilled nostrils in the mannequins and inserted nasal tubes that were connected to a home oxygen tank.
The oxygen flow was set at two liters a minute, which is similar to the level used in home oxygen therapy. When the mannequins were exposed to sparks, the oxygen tubes on the one with facial hair ignited and the mustache went up in flames. The oxygen tubes on the mannequin without facial hair did not ignite.
The Mayo Clinic team also analyzed clinic records and found that nine men were treated for home oxygen therapy-related burns between 1994 and 2013. Eight of the men had facial hair when they suffered their burns.
Patients in such cases "can have very bad facial burns and airway burns also," study senior author Dr. Andrew Greenlund said in a Mayo news release. "When fire burns the airway, then you have swelling and tissue death. It can be very dangerous."
The study was recent published in the journal Mayo Clinic Proceedings.
More than 1 million Americans use home oxygen therapy, and doctors need to warn patients about the burn risk associated with facial hair, the researchers said.
There are a number of potential sources of ignition, including people lighting matches or smoking cigarettes.
"It can be what you might think are innocuous or benign things," Greenlund said. "But with the facial hair and oxygen, it can be a real risk."
People using home oxygen therapy can reduce their risk of burns by shaving facial hair, using water-based hair gels instead of those with alcohol or oil, using humidified oxygen and by avoiding sparks and flames, the study authors said.
The American Association for Respiratory Care has more about home oxygen therapy.