According to Consumer Reports, air fresheners, candles and incense should be avoided in a house with anyone who has serious allergies or asthma.
Consumer Reports tested and evaluated portable home air purifiers with filters and rated the Whirlpool AP51030K, about $300, the best. Following is a short list of their other top rated brands with prices:
Hunter 30547—@ $260
Blueair 503—@ $600
GE AFHC32AM—@ $350
Blueair 650E—@ $800
Holmes HAP756-U—@ $146 (interestingly, this brand also has the lowest operating cost, too)