In my opinion, it doesn't matter whether it's paracite, bacterial, viral, whatever. He should just treat it. He may want to do it diluted.
Saline solution is another option.
There is just no comparing it to the bulb syringe or the neti pot. This is based on Bernoull's principle. As the water flows past a narrow opening, it creates a vacuum that pulls the material out of the sinus. Because of the pumping action of the Water Pik, this is accomplished much more effectively, which is why 20 minutes after irrigation the saline starts to come out the sinus cavities. You can improve effectiveness.