I'm not a hen BUT, I got a stick in the eye minor injury - but, eyes tend to hurt much more than the wound would suggest. The doctor decided to try something new on me. She put Cipro drops in and bandaged the entire eye. Then sent me to my pharmacy with a prescription for Cipro. In the half hour it took to get to pharmacy, I was telling the Pharmacist my eye was itching me terribly, no response from him.
Got home and took off eye patch as doctor had directed me to do and saw how badly my eye was swollen. I called and the Dr. answering service got the message to her. When she called me I told her what was going on. She said the drops she had put in were probably sufficient - not to use any more Cipro and just leave the eye alone.
She said she could have used a different med but wanted to try out the new Cipro. Great. I got to be her guinea pig. Afterwards the eye healed uneventfully but, I'll never forget the horrible itching and discomfort it caused. Since that time I had made sure all my doctors and dentist know I am allergic to Cipro.
It scares me to think what would have happened if I had taken Cipro orally for some other problem.
I just mention all this because I'm sure some chickens could be allergic to it also. I'm sure others may disagree with me but, I prefer a doctor take a more conservative approach and first tries an old familiar antibiotic instead of starting with the BIG guns and letting patients deal with the aftermath.
Years ago we had to take a week old puppy to the vet, he said it had pneumonia and gave it a penicillin shot. By the time we hit the main road, the puppy was unresponsive and we rushed back to the vet. Turned out the pup was allergic to penicillin - who knew??? If the vet had suggested we stay in the waiting room for 10-15 minutes we wouldn't have had to rush back with our hearts in our mouths. He ended up dying a short time later.
I guess what I am trying to bring out, if your chickens, dogs, cats, kids, get an injection or some new antibiotic please observe them for awhile to see that they don't go into shock, etc.
Much better to err on the side of caution than find discover a tragedy later. Off my soap box.