I did a ewr-hnl run 2 weekends ago and a double RT transcon this past weekend. Woke up Wed night with congestion and have been feeling lousy yesterday and today. If I had another run this weekend, I would postpone. I've seen people ignore colds and come down with bronchitis and pneumonia.
Then again, my brother, internal medicine MD, told me today that his office is mobbed by people suffering from allergies.