So we have a banty White Sea-bright hen (Mrs. CB) that sneezes every winter time. Its a slight little "ptooee" noise, with no white discharge or foam, and sometimes she breathes with her beak open, but not very often. She only sneezes in the winter; we've had her for 3 years now and her symptoms have not gotten worse. As soon as it gets cold out shes sneezing again. She seems to sneeze less when she's outside than when shes inside. I gave her antibiotics and also treated the whole flock, but no one else ever sneezes and she didnt stop sneezing. Is this a sickness or could it be from a dusty coop? We board up the windows in the winter and the only opening is the door to the run, and our coops doesnt have any vents or openings for air circulation. I clean the coop at least once a week and i try to air it out daily. Anything else I could do?