In a healthy human, the breath alternates between left and right nostril throughout the day. The pattern can vary but one nostril is typical dominant for about 88 minutes, followed by only two minutes where there is equal air entry through both nostrils and then it switches to the other nostril.
The nasal cycle was studied and discussed in the ancient yoga literature as well as in modern western literature it was first described by the German physician Richard Kayser in 1895.
The nasal cycle is controlled by the central nervous system. This is different to breathing more from one nostril due to a nasal congestion such as hay fever, sinusitis or a common cold.