Try North American Herb & Spice Wild Oil of Oregano capsules when you feel a cold coming on. I swear by it in the winter months. You should not take it long term (meaning all winter; daily), but it both fights off an oncoming virus and protects me from catching what comes home with my M.D. husband. I call it my "Shield". Go for the capsules, since the liquid tastes like I'm chomping on pine needles.

2/day if I feel sick already. 1/day if I am trying to avoid getting sick. Since I started taking it when I travel, I no longer catch a cold from the plane. I always did before, it seems.