Dejibo, I forgot to say that pollution in the house could be doing this. You were OK on
vacation. In the house you know the main possible culprits? New rug or rug pad, new furniture with stain resistant spray, new cabinets which have formaldehyde not yet outgassed (we had to coat ours with Environmentally Safe stuff) room freshener, gas leaking, mold, and of course that pollen that is irritating you. Constant battle and sometimes it's hard to figure what. Ours was primarily formaldehyde in new rug--had the whole house tested.