Raccoons are generally pretty harmless and cute, but there are two main dangers:
Unless rabid, raccoons won’t attack people or animals… unless they are cornered. You don’t want you or your dog/cat to be attacked by a raccoon, as they are smart, quick, and have very sharp teeth and claws.
Some raccoons can carry a roundworm that can cause Baylisascaris in humans, a disease whose symptoms aren’t fully described in the link above, which can include a not-fully-treatable potentially-coma-inducing brain infection . It’s a low risk but a bad one – if you find a raccoon nest on your property, you may want to consult CDC about how to thoroughly clean it up.