The vagina is a canal that connects the uterus to the outside of the body. Just outside the opening of the vagina is an area called the vulva. The vagina and vulva are home to many types of bacteria and other tiny organisms. The natural balance in the numbers of these organisms keeps the vagina healthy. If this balance changes, a vaginal infection may result.
A Healthy Environment
In a healthy vagina, many types of bacteria are present. The most common type is lactobacillus. These friendly bacteria help keep the vagina acidic (at a low pH). A low pH environment keeps bacteria that can be harmful from taking over. As long as the numbers of other types of bacteria stay in balance, they don't usually cause problems. Small amounts of yeast may also be present without causing problems.
Normal Vaginal Discharge
Vaginal fluid (discharge) is part of a healthy vaginal environment. Healthy discharge can be clear, white, or yellowish. Most women find that discharge tends to vary in amount and color. These changes are a normal part of the menstrual cycle.
An Unhealthy Environment
A vaginal infection may result when the normal vaginal environment is disrupted. This can be due to a change in the vaginal pH, increase in the numbers of a vaginal organism such as yeast, or infection by an outside organism.
- Bacterial vaginosis (BV) is due to an imbalance in the bacteria that are normally present in the vagina. The numbers of lactobacilli decrease and the numbers of certain other types of harmful bacteria increase.
- Candidiasis (yeast infection) occurs when yeast in the vagina increase and start attacking the vaginal tissues. Yeast is not bacteria, but a type of fungus. These infections are often caused by a type of yeast called Candida albicans. Other species of yeast can also cause infections.
- Trichomoniasis (often called "trich") is caused by an organism that is passed from one partner to another during sex. Men with trichomoniasis often don't have any symptoms. The organism can live and grow in the vagina for weeks or months before symptoms appear.
