Debby, You could make yourself go nuts by trying to approach every angle. Maybe you should check some allergy sites.. I do know people who've gotten rid of wall to wall carpet because of allergy issues. I never thought it was related to mites..but if they are a common problem.. then mites, mold, mildew and dust are all top allergens.. Fortunately I'm not sensitive to these ...yet anyway. My area people commonly develop newer allegies as they get older. More often than not, it's the hayfever or seasonal type to grasses or tree pollens.
I know my hose detaches from my machine..(but my machine does use bags) I think it would be pretty easy just to hose it out. I mean the mites need skin cells to feed on.. I used to put moth balls in my vacuum bag... as I had heard it would help kill fleas in the carpet. Then I heard that can actually be harmful to people. Fortunately no flea problem right now. My carpets are very old.. I steam clean them once a year. But they really need replacing. My upstairs does have wood floors under the carpets...but hubby likes the carpeting.. Maybe I should find some good articles about dust mites and forward them to him! Can't hurt! Might be able to get my hard wood floors sooner rather than later!
