Sometimes on Shabbos I get bad sinus pain (which sometimes just hurts and sometimes makes me feel sick and even feverish.) The thing that helps the most is neti pot (dissolving some salt in water and pouring it in one nostril.) Is it permissible to do this on Shabbos, or is there a problem with refuah, or with making salt water? Thanks in advance!
Both of your concerns are very valid. A person may only take medications if the pain that they have is considered choleh kol gufo, meaning that the condition makes the persons whole body weak, and the person has to stop what they are doing. Therefore it will depend on each time you have these sinus pains.
Regarding making the salt water, it is always better to make the salt water before shabbos, (and if you get these pains often you can make the salt water and save it, so it will be available when it is needed. However if it wasn’t made before shabbos, it can be made, but only the amount that you need for one use. The reason for this is because when making a large amount, it appears as if it is being prepared in order to salt things. There is a preference, to make it with a shinui, by adding the salt to the water.
O:CH 328-1 321-2, M:B 321-9, 473-21, Piskei Teshuvos 328-68, Chayei Adam 130 Dinei HaSeder B’ktzoro-1.