In addition to all the vaccuming and cleaning, advice, I have a fellowes aeramax air filter, and that really does help.

Not cheap though, actually a lot more than I paid for it, and needs about £60 in filter replacements a year running 24/7.

May be that it is outdated and there could be a more modern equivalent. The important thing is how much air it filters an hour, at least according to the blurb, and it has been amazing for my allergies.