What Could Be The Cause Of Itching And Irritation On The Genitals?

we are couples, last two days my wife got itching and iritation on her genital part. today we visited the doctor and diagniosed with fungus on vagina. prescribed with nuforce-3 kit for both of us. she got vagina suppostry. Doctor what could be the cause of this problem, in future to take precaution. thanks