What Causes Vaginal Itching?

Hi , i randomly get itches in my vagina( mostly labia area ) and when i scratch i have “dirty” in my finger nails, its brown ish & i researched and saw it could be accumulated discharge , but its been going on for a verg long time where especially in the night it itche, i dont know if its a bactera, yeast infection, should i treat it? What should i use ? Apple cider ? Special creams ? Please help .