In addition to a dust mite pillow cover and mattess cover, get a dust mite duvet/comforter cover
http://www.allergycontrol.com/store/...EXUKRKASJ5AN83
(you can also use this companies mattress covers as a duvet cove, it's a bit cheaper)
use a bottom sheet and the duvet cover, wash the covers (pillow and duvet), bottom sheet in Hot water once a week.
these are expensive compared to Kmart ones but they last many years longer, I think they have a lifetime guarentee.
this combo plus a hepa filler really helps because I can't dust really.