Why does the rinse have to be isotonic or hypertonic – rather than hypotonic? Thanks.

The Isotonic solution has the same concentration of salt as the normal cells in the body and should provide a soothing rinse. Some physicians do recommend Hypertonic solutions in certain cases. They believe that a higher concentrated solution will draw the fluid and mucus out of congested nasal passages and maybe sinus openings. A Hypotonic solution is more diluted and will generally cause burning or stinging in the nasal passages. We do not recommend using a hypotonic solution.