I'm not a medical type but I do have bad allergies......I usually let my body tell me how I feel about the bike. I commuted all winter with on/off sinus infections, as long as it wasn't in my chest and I wasn't coughing. I just kept in mind that my rides would be slower and I would need to be sure I got plenty of rest. My daily commute is only 12 miles tho, I never did any long rides during that time (too cold lol).
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"