There is some (inconsistent!) evidence that zinc acetate (but not gluconate) lozenges used in the very early stages of a cold can be effective.

I've had good results - but maybe those scratchy throats would have tuned out to be nothing, after all (sort of the opposite of a RCT).

If you decide to go that route, your zinc-to-copper ratio should be between 2 and 15 to 1 (more zinc than copper). The lozenges / dosage I use is around 150mg/day zinc, so copper's important. Also, it's important to use them as lozenges, not just swallow them (systemic level vs that in epithelial cells bathed in saliva).

Just my (possibly relevant) anecdata...