ELI5; How does Penicillin work?

Question

I understand a vaccine, a small dose of ‘x’ is given so your body can realise it’s foreign and learn how to fight it when the real thing comes.
But surely with a penicillin dose not being a vaccine,the body now has both it AND the foreign body to deal with? How does it’kill’ the intruder and not detrimental to the immune system?

Edit; Added words for clarification.

Edit 2; Thanks all, I have an understanding now!

In: 6

Answer 1

What others have said about penicillin directly disrupting the cell wall of bacteria is true. They don’t rely on the immune system to destroy bacteria.

As far as interactions with the immune system, people can become allergic to penicillin as they get sensitized to repeat doses. The most common such reaction is a rash, but penicillin allergies can escalate to even more dangerous reactions, including anaphylaxis.