The cause depends on the type of vaginitis you have.
Bacterial vaginosis results from an overgrowth of one of several organisms normally present in your vagina. Usually, "good" bacteria (lactobacilli) outnumber "bad" bacteria (anaerobes) in your vagina. But if anaerobic bacteria become too numerous, they upset the balance and bacterial vaginosis results. This type of vaginitis can spread during sexual intercourse, but it also occurs in people who aren't sexually active. Women with new or multiple sex partners, as well as women who douche or use an intrauterine device (IUD) for birth control, have a higher risk of bacterial vaginosis.
Yeast infections occur when certain internal or external factors change the normal environment of your vagina and trigger an overgrowth of a microscopic fungus - the most common being C. albicans. A yeast infection isn't considered a sexually transmitted disease. Besides causing most vaginal yeast infections, C. albicans also causes infections in other moist areas of your body, such as in your mouth (thrush), skin folds and fingernail beds. The fungi can also cause diaper rash.
Factors that increase your risk of yeast infections include:
Medications, such as antibiotics and steroids
Hormonal changes, such as those associated with pregnancy, birth control pills or menopause
Bubble baths, vaginal contraceptives, damp or tightfitting clothing, and feminine hygiene products, such as sprays and deodorants, don't cause yeast infections, but they may increase your susceptibility to infection.
Trichomoniasis is a common sexually transmitted disease caused by a microscopic, one-celled parasite called Trichomonas vaginalis. This organism spreads during sexual intercourse with someone who already has the infection. The organism usually infects the urinary tract in men, but often causes no symptoms in men. Trichomoniasis typically infects the vagina in women.
Vaginal sprays, douches, perfumed soaps, scented detergents and spermicidal products may cause an allergic reaction or irritate the delicate skin of your vulva and vagina. Vaginal itching and burning can also result from thinning of the vaginal lining caused by a drop in your hormone levels after natural menopause or surgical removal of your ovaries.