Isotonic or hypertonic salt solutions, potentially buffered with baking soda, can be used for nasal irrigation.

“i love the idea of isotonic or hypertonic salt solutions and just some people know we're talking about you could even take filtered water and boil it right and then cool it to make your own sterile water and then if you were i guess maybe in the show notes i'll try and put some resource for people so that they know how much salt to add um as a as an isotonic or a hypertonic a point nine or a three percent salt solution per like liter of water so you could do that and then usually people put a little bit of baking soda in i think to make it buffered at least a little bit”