Mixing 1 packet (1/2 teaspoon) of salt with 8 ounces of warm water creates a physiological saline solution. This solution is now isotonic - 0.9% salt content - which is the same salt content the body naturally produces. Using an isotonic saline solution is important for several reasons: • It does not disturb the natural production of salt in the body. • An isotonic saline solution prevents a stinging sensation when rinsing the nasal cavities. If too little (hypotonic) salt or too much (hypertonic) salt is used, a slight stinging sensation can be experienced when rinsing the nasal cavities. • Mucous membranes tend to absorb water from the saline solution when it contains less than 0.9% salt. Hence, you may experience swelling of the mucous membranes. Conversely, using a little more salt (which is sometimes recommended by doctors) tends to shrink the mucous membranes slightly. This improves breathing by allowing air to better flow through the nostrils.