I keep chickens and a while back six of them suddenly got swollen faces, the younger of the six seemed the least effected by it. If only one side of its face swelled then once the swelling went down then the other side of the face would bloat up as well. I immediately separated them from the rest of the flock at the bottom of our garden and let them be. Nobody else showed signs of infection until recently when one of my hens in a cage at the top of the garden got it (just her) and one of my chicks who I had been just starting to let outside. None of the chickens closest to the infected got the disease and neither did the chicks siblings though I did separate them. There is no awful smell and their eyes did weep a bit though once the swelling went down there was no other symptoms. During the period they showed swelling they acted no differently than they did normally except being briefly blind on one side. I did notice some rasping in mornings and afternoons but they don't do that anymore, nobody perished either. I'm not sure about laying eggs because the disease coincided with their molting. I have tried changing water, food and kept them clean so I have no idea how it's spreading and nothing I found on the internet seemed to quite fit. The chicks swelling went down in a day and the older hens and one rooster's swelling took a couple of days to go down. Does anyone have any ideas at to what it is and what I can do to prevent it?