Is it true there is a mediction called alum to shrink your vagina?

YES! YES! and YES! You can buy the powder or the rock, or sometimes in forms of crystals either one will do the trick. You just get a bit put it in warm water and wash your vagina. Dissolve the crystals/rock/powder fully. It works immediatly but dont do it too often as it can dry out your vagina. Maybe one a month.