One of our Buff Orpingtons got Bronchitis two months or so ago. We put medication in her water, but it didn't seem to be working. After a while, we just took out the medicine and put in apple cider vinegar. It was either time or the apple cider vinegar that cured her.
Your chicken might sneeze a lot, may look and act tired sometimes, and the eye might end up looking pretty bad, meaning swelling or a
heavy amount of bubbles. These symptoms occured in our chicken. Also, you might see traces of the swelling even after the sickness.
This is an illness that just runs its course. All you can really do for it is put in some apple cider vinegar, or some medicine that you put in the water.
Be aware, the sickness is contagious, and it can stay for a while!!