Why do i get yeast infections when i take antibiotics?

No bacteria left: Antibiotics kill bacteria. A woman's vagina has bacteria in it that are actually meant to be there and prevent yeast in the vagina from growing too much and causing symptoms of a yeast infection. When you take antibiotics the level of these 'good' bacteria in the vagina drops which allows the yeast in the vagina to grow too much.

Microflora imbalance: The antibiotics kill much of the normal healthy bacteria and allow the fungi to take over. This imbalance of the microflora causes the yeast infection. You may be able to prevent yeast infection outbreak of you use an antifingal vaginal cream while taking the antibiotics.