Elderberry works wonders! We found it in Amsterdam in 2016. I caught the flu on the plane over for SteemFest. It's a good as a preventative during cold/flu season and great to shorten illnesses when you're already sick. I also use this grapefruit seed extract nasal spray before/after I fly or am exposed to a sick person. They say if you flush out your nasal cavities with this no more than three hours after exposure you can sometimes prevent yourself from getting sick.