A vaginal yeast infection, also known as candidiasis, is a common fungal infection causing irritation, discharge and severe itching in the vagina and the vulva, the tissues at the vaginal opening. A healthy vagina has bacteria and some yeast cells. But when the balance of bacteria and yeast changes, the yeast cells multiply and cause infection. Although vaginal yeast infection isn't considered as a sexually transmitted infection, there's a high risk of vaginal yeast infection at the time of first regular sexual activity. Medications can successfully treat vaginal yeast infections. If you have recurrent yeast infections, like four or more within a year, you are required to go for a longer treatment course and a maintenance plan.