I’m not a health professional but I think, as long as you’re keeping yourself clean and the panties are clean, then yes, it’s safe. I’ve never known anyone have a problem with it.
As with anything you’re putting in your pussy, such as a tampon or dildo or a penis, you want it clean or you risk a bacterial infection, but actually your vagina is most extraordinary and very good at keeping itself healthy.
If you’re a virgin then stuffing panties in might damage your hymen so you’d bleed a little bit.
Don’t leave anything in there for too long (but we’re talking days, not hours) or you risk toxic shock syndrome – and if it were a penis it would be very inconvenient too. And if you use multiple pairs, make sure you count them in, and count them out!
But generally, it’s a nice safe, fun kinky experience that everyone can try! So go for it!
The other two rules being don’t put anything in your pussy that’s been in your bottom, and don’t use anything containing sugar as that is just asking for a yeast infection.
No one hung Candy Canes on the Christmas tree after last year’s little trip to the ER.