A non-drug nasal spray could theoretically help stop the spread of respiratory viruses like the flu and COVID-19 better than wearing a mask, a new study suggests.

The spray uses ingredients that are medically inactive to trap germs in the nose before they can infect a person, researchers said.

“We developed a drug-free formulation using these compounds to block germs in three ways,” said co-senior study author Nitin Joshi, an assistant professor of anesthesiology at Brigham and Women’s Hospital in Boston.

The nasal spray “forms a gel-like matrix that traps respiratory droplets, immobilizes the germs, and effectively neutralizes them, preventing infection,” Joshi explained in a hospital news release.

Researchers call their discovery Pathogen Capture and Neutralizing Spray (PCANS).

Most viruses enter the human body through the nose. Vaccines can help the immune system fend off an immune attack, but they can’t stop the attack at its source, researchers noted.

“The COVID pandemic showed us what respiratory pathogens can do to humanity in a very short time. That threat hasn’t gone away,” said co-senior study author Jeffrey Karp, distinguished chair in anesthesiology at Brigham and Women’s. “Not only do we have the flu to deal with seasonally, but we now have COVID, too.”

Using a 3D-printed replica of the human nose, researchers showed that the spray captured twice as many droplets as would be trapped by natural mucus.

“PCANS forms a gel, increasing its mechanical strength by a hundred times, forming a solid barrier,” explained lead researcher John Joseph, a former postdoctoral fellow at Brigham and Women’s. “It blocked and neutralized almost 100% of all viruses and bacteria we tested, including influenza, SARS-CoV-2, RSV, adenovirus, K Pneumonia and more.”

Experiments in mice showed that a single dose of the spray could effectively block infection from a flu virus at 25 times the lethal dose, researchers said. Essentially none of the virus made its way into the lungs of the mice, and the mice didn’t develop any immune responses like inflammation.

“In a rigorous mouse model study, prophylactic treatment with PCANS demonstrated exceptional efficacy, with treated mice exhibiting complete protection, while the untreated group showed no such benefit,” said co-senior study author Yohannes Tesfaigzi, a professor of respiratory and inflammatory diseases at Brigham and Women’s.

The spray now needs to be tested in human clinical trials, researchers said. The team also is investigating its potential for allergy relief, to see if it can block allergens as effectively as viruses.

The new study was published recently in the journal Advanced Materials.