Seven years ago, I presented an oral communication “Nasal breathing technique in nasal airway obstruction. Viral infections in upper respiratory tract”, in the 20th World Congress of the International Federation of Oto-Rhino-Laryngologycal Societes, IFOS, Seoul, 2013. This is a technique based on physiological concepts of breathing, to avoid the use of nasal decongestants in a cold or flu. We have to breathe the air we exhale. It is air with a high concentration of CO2, but it is not toxic. Inhaling carbon dioxide in the air we exhale through a nasal mask made by ourselves, using our hands, acts as a nasal decongestant. I think it is possible that this breathing technique can inactivate the flu virus, because the people who used it (10 patients), did not develop the flu in these years.