Re: Why gargle with saltwater?

Gargling with salt water helps to kill bacteria and prevent infection.
The salt water sets up a hypertonic environment; water rushes out of the
bacterium by osmosis, killing the bacterium.  So it is not a question 
of pressure exerted on red blood cell walls, but rather the pressure
exerted on the bacterial cell wall.

What else is salt water good for?  Sterile saline (salt water) is used
widely in medicine to flush wounds, and a dilute solution is used to
treat contact lenses by matching the ionic strength of the fluids of the
eye.  Putting pure water in the eye along with a contact lens can be
very uncomfortable!