If you have central air/heating then you probably have a problem that might cause some discomfort for your guest. Before having house guest you need to make sure that your air duct systems are cleaned by competent professionals.
Here in Alexandria, La. I suggest calling Encore.
Encore will get your duct work cleaned and dust/bacteria free. It is not very expensive, much cheaper than a trip to the allergist.
Encore also does carpet cleaning. Why not get both done at the same time and get your home cleaned top to bottom.