Question: what causes bloked noses when we have a cold?

Martin – I think everyone naturally alternates left/right nostril breathing even when not having a cold. I don’t think it is known why this is.

This question is a good example of where google searching fails. You get swamped in the yoga technique of alternate nostril breathing and the pseudoscience that overlays discussion of left/right brain asymmetry (as people think the left nostril air feeds the right brain and vice versa).

So back to the old reliable medline for this reference. Apparently the mean cycle of left/right nostril breahing is 2 hours. But there is a lot of natural variability so – at least in this area Emily – you are not a freak!

Ohki, M., Ogoshi, T., Yuasa, T., Kawano, K. and Kawano, M. (2005) Extended observation of the nasal cycle using a portable rhinoflowmeter. J Otolaryngol. 34, 346-349

OBJECTIVE: Nasal patency varies owing to the effects of humidity, temperature, and exercise. In addition, periodic cycles of congestion and decongestion that alternate between the right and the left side of the nose, which are termed the “nasal cycle,” have been observed. The physiologic mechanisms underlying this cycle are not clear. Sympathetic nerves that supply the nose are regulated by the hypothalamus and the vasomotor areas of the brainstem. It is possible that the nasal cycle could be involved in protection against respiratory infection or allergies. Conventional methods of studying the nasal cycle, including rhinomanometry and acoustic rhinometry, impose limitations on the location and timing of evaluation. We studied the nasal cycle using a new portable device for relatively long-term rhinoflowmetry. METHODS: Twenty normal subjects aged 24 to 77 years were fitted with the portable rhinoflowmeter (Rhinocycle, Rhinometrics, Lynge, Denmark) to continuously measure nasal air flow via each nostril over 12 daytime hours. RESULTS: No subject complained of discomfort owing to the device, and 14 of them showed a detectable nasal cycle. The mean nasal cycle duration was 110 minutes, although variation was considerable, even in a single subject. CONCLUSIONS: The portable device proved useful for observing the nasal cycle, and it should be valuable for the general investigation of nasal physiology.