The so-called alternating nasal congestion refers to the alternating blockage of the left and right nasal passages and is mainly related to the nasal cycle and chronic rhinitis.
In a normal person, the nasal cavity has three turbinates – upper, middle and lower – which are covered with a mucosal layer rich in blood supply. The state of congestion of the mucous membrane of the inferior turbinates is alternately and regularly contracted and dilated (a cycle occurs in about 2-7 hours), which manifests itself as a regular and alternating change in nasal resistance from day to night and from left to right. This is the nasal cycle, also known as the physiological turbinate cycle. The presence of the nasal cycle encourages humans to turn over repeatedly during sleep, adjusting their sleeping position and helping to relieve fatigue.
Alternating nasal congestion due to the nasal cycle is a very normal physiological phenomenon and is generally nothing to be overly concerned about. However, if alternating nasal congestion occurs along with sneezing and runny nose, it should be considered as chronic rhinitis and active treatment is required at this time.