According to research, during the congestion phase, the nasal passage's ability to let air through decreases. Researchers state that the nasal cycle causes the two nostrils to alternate control of airflow approximately every two hours while awake, whereas the switching is less frequent during sleep. Even in good health, one nostril appears to be more capable of passing air than the other, a phenomenon known as the nasal cycle. This was the conclusion of a study by British researchers from Lancaster University. This process consists of two phases: congestion and decongestion. «Science Alert» notes that one of the most annoying things about having a cold or seasonal allergies is a stuffy nose, which makes breathing difficult or nearly impossible.
