Yeast infection is a very common cause of vaginal infection. It is caused by a form of yeast known as candida. Candida occurs naturally in the vagina and bowel, and usually it is no trouble because it is kept in check by other, harmless bacteria which inhabit the same places. However, if these bacteria are reduced-by antibiotics, for example-the yeast can grow and cause problems.

Pregnant women and those with diabetes often get yeast infections, and it is most likely to appear just before a period. Ask your doctor about a one-dose medication that treats yeast infections.

Symptoms: A thick white vaginal discharge that looks like cottage cheese. Irritation and itchiness around the vagina. Discomfort when urinating and during sexual intercourse.

Trichomonas is a tiny parasite that may be transmitted during sex or picked up by contaminated washcloths or towels. Men can get it too, but rarely show any symptoms. Because their symptoms may be hidden, it is necessary for men to be treated for trichomonas at the same time as their partners, so the disease is not passed back and forth.

Symptoms: Itching, soreness, and a burning sensation in the vagina. Foul-smelling, discolored vaginal discharge.

Chlamydia is a sexually transmitted disease that may cause symptoms in both men and women. It can lead to urinary infection or fertility problems if not treated.

Symptoms: Watery, sometimes odorous, vaginal discharge. Pain during urination.

Gonorrhea is a bacterial sexually transmitted disease. It is very infectious.

Symptoms: Possible slight white, green, or brown discharge. Men have a discharge, swelling, and pain when urinating.

Cervical Erosion: Sometimes a small area on the neck of the uterus (cervix) becomes raw and oozes. It may cause a heavy, clear, odorless discharge. Sometimes there is a little blood. The discharge tends to be worse just before a period. Bleeding after sexual intercourse is also common in this condition. Cervical erosion can be treated by minor surgery.