An article in the New York Times reported that humming can ease sinus problems and asthma. There is good evidence to show that this is true. Researchers in Sweden looked at airflow between the nose and sinuses and specifically, the amount of the gas nitric oxide made by the sinuses that can escape into the nose while humming. This is because humming causes the air to oscillate between the sinuses and nose even if the sinus drainage pathways are narrowed. The researchers showed that during humming the amount of nitric oxide escaping into the nose increased 15-fold. They theorized that some of the trapped sinus secretions escape along with the nitric oxide causing infection to resolve.
What the Times article did not discuss is why nitric oxide is important to asthma. Nitric oxide is a natural bronchodilator and when the sinuses are draining normally, the gases made there flow into the lungs keeping them healthy as well. If the sinuses are blocked, the lack of nitric oxide in the lungs can lead to asthma-like reactions.
While it is possible that the sinus blockage could be severe enough to overcome the effect of humming, in many cases humming can increase the drainage of the sinuses reducing both sinusitis and asthma in susceptible patients. Whether humming alone is sufficient to treat sinusitis or asthma has yet to be shown, but most patients probably need other treatments in addition to treat their condition.
If you think you have sinusitis and/or asthma be sure to visit a sinus/ allergy/ asthma specialist. And keep on humming!