I have found two herbs that have really help eliminate my upper respiratory systems as long is it not a bacterial infection:

Horehound: Dry or tea, several time a day. Watch for dry skin or eyes.

Fenugreek: Get at Health Food Store. Take 1-2 capsules, several times a day if needed to control symptoms.

These won't get rid of a sore throat or actue infection but dry your congestion it will do.

From the trenches,
Celeste