I don't want to be a downer, but there's a thread right now about HFCS (which is what Karo is) containing mercury. It seems to be accurate. That might be something a person would want to weigh the risks of before pouring into sinus cavities... Otherwise, thanks for the recipe! Maybe without the syrup?
I had no idea. You can certainly use it without the karo. I think it just soothes the tissues to keep the salt and baking soda from burning. Maybe a touch of honey instead?