We have 2 of the big tall ones. I keep one in the bedroom running 24/7. It is easy to clean. Just pull it out and wipe down the shafts with the cloth that came with it. It DOES have to be dry before you put it back in the tube, but doesn't take more than a few minutes. I do think it helps with allergies. I am very allergic to cats and right now have 2 in the house. (yeah, I know!) They are shut out of the bedroom during the day and I do find that I am able to breathe more easily when sleeping. They were expensive-nearly $250 each. It included a "free" one for the bathroom which I am not impressed with.