Since I have overall improved my health after I had my dental amalgams removed, I rarely get colds. To help me detoxify my body (even before I linked my health problems to the dental amalgams), I switched to a healthy diet of non-processed foods.
Now with healthy foods, rich in fruits and vegetables, I rarely get colds or the flu. I used to catch "every virus on the planet" previously.

I had to tell people to stay away. I didn't need another cold.
These days, if in the rare case, that I catch one of these viruses, I find that raw garlic (one or two cloves daily), helps knock it out. One time, I was sick traveling, instead of carrying cold medication, I took my raw garlic with me. The raw garlic kept me well enough for me to accomplish my task while traveling. Dried fruits, for some reason, seem to neutralize the garlic odor somewhat too - so I bring dried apricots with me also to take the next day in the morning - after taking the garlic about 12 to 18 hours earlier. Raw (non-cooked) garlic is a natural antibiotic.