I am not a doctor, nor do I play one on T.V., but I do have a little something up my sleeve that I swear knocks out the common cold, or at least significantly shortens its nasty little stay. My remedy consists of a 1, 2 punch.
Punch 1: The Neti Pot
O.K. I admit that I have, on occasion, watched an episode of Oprah. I am not one to worship at the shrine of Oprah and may be just a bit jaded about the show after this experience in her audience ( and, no, I am not bitter just because I fully expected it to be the "Favorite Things" show). However, you can find an interesting tid bit or two now and then, and it sure does help to pass the time on the treadmill. It was during such time passing, that I saw an episode with Dr. Oz that sang the praises of the Neti pot. It is a sinus cleansing system, in which you pour a saline solution from the pot into one nostril until it starts coming out the other side. Then you repeat the process on the other side. I'm not gonna lie, it is not the most comfortable experience in the world, but it really does do the trick. Even my 10 year old son swears by it for relief from his seasonal allergies. So, as soon as you feel the cold start to come on...start the Neti pot at least once a day unitl symptoms subside.
Punch 2: Crystalized Vitamin C
Stir a teaspoon into a small glass of orange juice in the morning, again, as soon as symptoms start. Repeat for 2-3 mornings, or until symptoms dissapate. Warning...it is VERY sour, so I recommend stirring it into as small a glass as possible and drinking as fast as possible, followed by just some straight orange juice. Warning #2...it will clean you out (potty wise) so just be prepared for that little side effect. Warning #3...because of the cleaning out effect I don't recommend this step for kids. Just lots of orange juice for them!
When done at the first symptom of a cold it has knocked it out within 2-3 days for me without ever getting to the full blown cold stage. Hope maybe it will help you too.