Is neosporin safe to use when streatcheing ear piercings and for aftercare?

Not at all. You don't want to use any ointments or even creams when stretching. The stretch can't breathe and then they start to stink or get infected. The ointments also catch gunk floating in the air. You can use extra virgin olive oil or vitamin E oil to stretch. For aftercare, just clean with natural sea salt and water. If they get dry, you could use the vitamin E oil.