I just finished reading Ed Pavelka's book "900 All-Time Best Tips". A hundred and something pages with tips to enrich the experience of long-distance cyclists.
Tips include -among other things- nutrition, long-rides, mountain biking advice.
The author answered to a "runny-nose" situation: "I do not suffer from any seasonal allergies but get runny nose only when I ride on temperatures close to 20 oC". Pavelka explains that a runny nose (similar to having a cold) may be due to vasomotors rhinitis (Pavelka, page 82). I was glad to find an answer to my four-year-old question.