What Causes Itching In Vulva And Clitoris?

I am a girl. For the last few months i am having constant itching in my private parts specially the vulva and the clitoris. I have not been sexually active for the last one year and this itch has appeared about 5months back. I have tried changing sanitary napkin brands but to no effect. Can you please help me. Its very embarrassing when the itch happens in public.