Hi, I slipped on Monday and fell flat on my back, rump and head. I had absolutely no adverse issues, except for severe embarrassment!, until today (Wednesday). Now I am starting to feel a bit of a generalized headache, runny nose, irritability ... however, on Friday, my doctor put me on Zyrtec and Flonase for allergies (although I really do not believe I have allergies!) .... so the symptoms could very well be that. I am only asking because I am flying tomorrow and want to be sure I am okay. I called my doctor, only to discover she is on vacation this week :-( Do concussion present two days after the fact? And, if they do, what should I be looking for?? Thank you!