In the springtime I suffer from some minor allergies. Years ago I found that during the worst times, taking ONE Benadryl tablet before I go to bed would help with the headaches, runny nose and itchy, red eyes, and allow me to sleep comfortably during the night. Last spring, however, I did not use Benadryl because it is a "Not Allowed Medication" (but ended up wishing I had some nights!). My question is what exactly does not allowed mean: NEVER allowed, NOT allowed while flying, or NOT allowed within a certain time frame? I am new in the aviation world and hopefully plan to spend many more springtimes flying. Any advise would be appreciated. Thanks!