Hi, I only just saw your posting, and it reminded me that I read somewhere that this happens so I did a quick search and found this, it is what Yogi's say.
"With this exercise, we breathe through only one nostril at a time. The logic behind this exercise is that normal breathing does alternate from one nostril to the other at various times during the day. In a healthy person the breath will alternate between nostrils about every two hours. Because most of us are not in optimum health, this time period varies considerably between people and further reduces our vitality. According to the yogis, when the breath continues to flow in one nostril for more than two hours, as it does with most of us, it will have an adverse effect on our health. If the right nostril is involved, the result is mental and nervous disturbance. If the left nostril is involved, the result is chronic fatigue and reduced brain function. The longer the flow of breath in one nostril, the more serious the illness will be."
[This message has been edited by Corinna_H (edited 10-09-2003).]