I had that quite recently during decorating works (even on completely different floors), assuming from dust and all sorts being brought up and being more vulnerable after having a cold and asthma (not that it troubles me much anymore). A colleague has been suffering really badly with their asthma because of it and has been signed off for a couple of weeks. Same for both of us, suffered at work, fine when not at work.
I was ok after a couple of weeks but now have another cold...argh...