I haven't tried that. One thing I recommend, though, is that you only take products containing echinacea if you are absolutely sure that you are not allergic to ragweeds. I took echinacea for a whole winter once, and got cold after cold after cold..... only to have my doctor (who works with alternative medicines) tell me that I should've asked her before starting an echinacea regimen... it can be detrimental to the health of people with ragweed allergies, because it is a member of the ragweed family.
What I DO take, however, is a product called Emergen-C, which is a sort of fizzing drink mix that is wildly popular among musicians, for some reason.... it helps keep colds at bay even when touring through different cities (thus different local germs and climates) each night, not getting enough sleep, and heavy smoke exposure.
I swear by it, I often tour with my S.O. and I haven't had a serious cold since I started taking it daily.