If you are a woman, chances are -- whether you have had or have a yeast infection or not -- you still may have yeast in the vaginal area at present. Your body produces a “good” bacteria that keeps yeast from overgrowing -- most of the time. Sometimes, things get a little off-balanced and this fungus (Candida) can result in a vaginal yeast infection.
What causes it? A series of things may cause this infection. For example, it can happen if your blood sugar is out of control, if your immune system is suppressed, or if you are taking antibiotics or certain medications. Even oral contraceptives can be the culprit.
How do you know if you have a yeast infection? The only sure way to know is to be tested by a doctor.
https://www.empowher.com/reproductive-system/content/what-girls-need-know-about-yeast-infections