I feed a small feral that has many open sores on her skin. I'm assuming they are from biting fleas. She is always nipping and scratching. These sores are very nasty looking. This cat has just started letting me scratch its head and neck and I am going to try to put some flea treatment on her neck while doing this. My question is can I also try giving some antibiotic in her food while she has this flea treatment on? Will there be any kind of adverse reaction? Thank you!