It's only been a week since he was installed in my office (7m2 without VMC or mouth extraction / ventilation above the window). I can not open the window to air often without sneezing because of the centenary poplars 3 meters from my window ...). There I opened a little more, the air is cleaner, less "heavy". Not yet felt any difference in terms of allergies, but it's not worse.
I will amend section a few times.
EDIT: here almost a year that I have little DX5. He still works as well. It does not necessarily succeed in removing odors, however it cleanses the air with pollutants such as pollen. I have many fewer allergies since it is installed in the office.