Machaon

You can pick up very good air purifiers at auction around the Internet for under $100.

I've got seven Hunter air purifiers at home, one, to two, in each room, most of which I picked up new, at auction, for about $60, including shipping.

I've also found that, during high pollen, high pollution days, wearing an earloop nurses mask helps me a lot. I sleep with one of these masks.