Antibiotics for chickens?

I wanted to get an antibiotic for my chickens but all the ones I looked at say not to give to egg layers. They don't say anything about not using the eggs for a certain amount of time, just not to use it. Several of my hens have lost some feathers around their rear and the skin looks really red. So I thought since I was tossing the eggs anyway due to worming them (they already had this problem before the worming) that I would go ahead and treat with an antibiotic and perhaps for coccidiosis since I don't use a medicated feed. One thing I didn't check was Terramycin crumbles, can you give this to chickens? Laying hens? Any suggestions anyone? Thanks, Lana