1. A yeast infection is due to vaginal inflammation in the presence of the yeast organism Candida.
2. You are more likely to get a yeast infection if you have a poor immune system. These immune changes can be at a local level directly related to how the vaginal environment fights infection.
3. there are certain species of Candida, including glabrata, that don't often cause what we would perceive of as a yeast infection, but can and this may be resistant to treatment.
4. You may be pregnant, hormone changes of all sorts seem to trigger extra yeast infections
5. You may have had recent antibiotics, this will decreases the healthy bacteria and make way for an overgrowth of other organisms including yeast.
6. You may have too low estrogen, healthy bacteria need to be able to have an environment that has the complex sugar glycogen in the lining cells to feed upon.