fresh ginger root in decoction (as dense as possible) is good for all the respiratory sphere -in ayurveda it is recommended for the median and upper sphere (hope my english terms are correct here). median is the area where digestion starts (end of throat, stomach), upper is lungs, throat, nose (all organs of breath). organic is the best choice, and not that expensive.
And it really works. of course there are other plants too.
you can also mix it with curcuma root or powder: curcumine is an interesting anti-oxydant and has indicated activity of regulation of the immune system (it is the kind of thing that really is useful when consumed regularly, like many spices).
And one or two tricks with a cold :
> wash the nose with physiological serum (or water boilt then cooled with a bit of salt added). the big problem with a cold is the relative infection and encumbered nose. it is way more comfy not to let it spread down to the throat and lungs. you can also choose to wash your nose regularly, just like you clean your teeth. but I guess it is up to everyone to see how far they want to carry their cleaning rituals
> another little useful thing is to clean the tongue : when you have a cold, lots of microbia deposit...on your tongue. you can easily find a tongue cleaner, or use a smooth toothbrush. again you can choose to do that every time you clean your teeth (I do it
those 2 tricks may seem strange if you have never heard of them, but... they are really worth trying, if not as everyday hygiene, at least to help with a cold.