Is penicillin dangerous to humans

Answer 1

Penicillin is penicillin, regardless of to whom - or what - it's being administered. There's no special feline version.

It's only harmful if you ingest a great deal of it or you're allergic to it.

Answer 2

Yes an no, penicillin, as you know, is a bactericide, it kills bacteria.

A great deal of your body's cells are bacteria.

Penicillin throws the ever-metaphorical spanner into the works, the human body does not function properly without bacteria, incorrect use could have you catching every which and what illness native to your country and dying.