A while ago I had one hen that had bubbles in her eyes and no other symptoms. After I gave her antibiotics her eyes cleared up and she has been fine until now (more than a year later). I noticed her face looks swollen and she has tiny bubbles in the corner of one eye. She doesn't sneeze, show any trouble breathing, or act different than usual. None of the other chickens are affected either, is it possible she could have some sort of allergy or is she sick?
She's sick. Probably the same thing as before since it rides around in a chicken for life. A chicken can become symptomatic again in times of stress. If you treated it with an antibiotic before, go ahead and use the same thing again. If you have no antibiotic, you can use Tylan 50.