Kate, praying for them; and I hope and pray they can find out what triggers this, usually some kind of allergy.
Until I was diagnosed as coeliac, for instance, I always had sinus problems. Since avoiding the appropriate grains, e.g. wheat, I’ve never had the problem.
Kate, it’s miserable for them and I know how helpless on feels when one’s family is suffering from sinusitus or any discomfort or illness, it’s very distressing. God bless and help your family in every way.