What point are you trying to prove with this link? Do you realise the first line on that link says that they do indeed work?
The rest of the article simply goes on to list some of the misconceptions people can have about air purifiers. I don't think anyone in this thread has suggested that buying one means you can sell your hoover, seal your windows, smoke like a chimney, or give up your antihistamines so I'm not sure how this article is relevant?
Out of curiosity, do you suffer with allergies? Have you tried an air purifier?
I've suffered with hayfever since I was a young child trying various things over the last 20 years or so it's caused issues for me. Whilst I've only had my air purifier a short time, despite being in the midst of the "pollen bomb" and super high pollen counts, I'm finding I'm having one of the best runs of not suffering with my usual itchy eyes and constant sneezing that I've had in years. I'm still having to take my antihistamine and yes I can still have effects when I'm out and about. But ultimately as someone who does suffer from allergies my early impressions are that this is having a positive effect.
If your an allergy suffer, have used one, and found it didn't work thats great. You would be adding a worth while opinion to this thread. But if all you are doing is typing "do air purifiers" work into google and venturing as far as link number two you aren't adding a great deal.