M.H.
yep, you have to add salt and then there will be no question as to when it is working. I use cold mist as well, the warm mist scare me! They get VERY hot and make the room VERY hot as well! The last time I tried to use it, my son's room reached about 90 degrees within minutes! The cold mist are great and they are recommended for the resistance to bacterial growth as well. Great in the summer because it will keep the room cool as well! I really dont' think it would do anything for allergies anyway?... I could be wrong.