For nasal irrigation devices, a sound approach must confirm distilled sterile or correctly boiled-and-cooled water, correct salt concentration, clean device condition, solution temperature, head position, flow or squeeze pressure, one-way drainage, symptom response, ear discomfort, bleeding, and frequency.
The sections below investigate the interpretation of results. It uses safe rinse water, isotonic saline, and flow pressure to explain what changes the outcome, where uncertainty enters, and which response is proportionate.