Doctors used to prescribe "sea air" for patients with respiratory infections. Science has proven that sea salt does indeed benefit respiration:
(URI = Upper Respiratory Infection.)
The sea salt-derived physiological saline nasal spray device satisfactorily improved nasal congestion, runny nose, sleep quality, and appetite in adults with URI, with no adverse effects.
– Efficacy and Safety of Sea Salt-Derived Physiological Saline Nasal Spray as Add-On Therapy in Patients with Acute Upper Respiratory Infection: A Multicenter Retrospective Cohort Study
The most impressive part of that is the last bit: "no adverse effects". Salt is a preservative, which explains the anti-microbial action.
I had lifelong problems with rhinitis and sinusitis, and couldn't tolerate the side effects of other treatments. Using a water nasal spray helped some, but adding sea salt made a dramatic difference. I can't actually tell whether a spray is salty without tasting it. However, with sea salt, symptoms simply never progressed to the usual infections. Over time the difference in comfort became obvious.
Cheap generic ingredients encourage liberal use at the first sign of discomfort. There's no reason to let irritants linger on your mucosa, so don't. Sea salt has healthy trace nutrients for humans anyway, so there's probably a benefit to getting a dose throughout the day.
Your eyes and sinuses are right next to your brain, so it's prudent to be extra careful. Buy a small bottle of distilled water, so it's easy to pour into the tiny spray bottle. The bottle will last months. This avoids tapwater contaminants such as chlorine.
72,344 Americans died of respiratory disease in 2019, before the pandemic. Lower respiratory infections are the 4th leading cause of death globally, and they obviously are often caused by upper respiratory infections. If we can institute a hygiene practice similar to washing hands but for the upper respiratory tract, it would save many lives.
Too bad it's not patentable, or Big Pharma would advertise it. I believe the medical cartel's efforts to deprecate generic competitors are the reason why subreddits such as Sinusitis, Allergies, Lifehacks and Lifeprotips downvote and remove this saline spray idea.