3 years ago I heard about a cold prevention product advertised on the radio called Airborne. I found it at the drug store and followed the directions. I have not had a cold since. It is easy to use and really has worked for me. I find it particularly easy to use on planes... you just need a little water to dissolve the tablet. It is not cheap - about $6 for 10 tablets, but it has been worth it to me.