Because girls' immunity is in a relatively low state during their official holidays, and at this time, things like potions are used to make their hair, sometimes they may get sick and catch a cold, and if there is a wound, they are more prone to inflammation.
This is why it is not easy to get wet in the rain or get pierced during menstruation.
Secondly, sitting for too long will be airtight and unsanitary.
So, just wait a few days until your period is completely clean.