Leo- Chinese Superstition

If you spread some cow's tears on your eyes, you will see the ghosts around you. But it is dangerous, because you may not be able to distinguish the ghosts and real humans. If a house always has some strange things happenning, like if some pets died for no reason, or if the householder was sick for long time since he moved to this house,  then we believe that there are some ghosts in the house, so we need an exorcism. Exorcists need to communicate with those ghosts, so they sometimes spread on some cow's tears on their eyes. Then he will find the ghost and do something to let that ghost stay away from the house.