Women dread the intense itching and thick, white discharge that signals the presence of a vaginal yeast infection. Candida albicans is the scientific name of the yeast that usually causes these infections. According to the Centers for Disease Control and Prevention (CDC), 75 percent of women will have at least one vaginal yeast infection in their lifetime. But the diagnosis of a yeast infection is a bit more complicated than simply having yeast in the vagina. Yeast can be present in or around the vagina and not cause symptoms, a situation known as colonization. Diseases like HIV and diabetes, certain medications and being pregnant increase the chances that an overgrowth of yeast will occur and cause the unpleasant symptoms typically associated with a vaginal yeast infection. While it is not considered a sexually-transmitted disease, like chlamydia or gonorrhea, some sex practices increase the likelihood of developing a vaginal yeast infection.
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Yeast in Your Vagina Is Often Normal
A healthy vagina normally hosts a large number of bacteria and sometimes yeast. As described in a September 2000 article published in "American Family Physician," Lactobacillus acidophilus is the primary bacteria in a healthy vagina and up to 50 percent of women without symptoms also have yeast in their vagina. Lactobacillus secretes hydrogen peroxide, which helps keep the vagina as a slightly acidic environment. This keeps other organisms in check, preventing their overgrowth. But a fragile balance exists in this little ecosystem. Diabetes, oral sex, pregnancy and antibiotics can alter the vaginal environment, sometimes sufficiently to allow other organisms such as yeast to overgrow and cause symptomatic infections.
Intercourse Can Introduce Vaginal Yeast
Sexual activity per se does not cause vaginal yeast infections. However, sexual intercourse can introduce yeast into the vagina, which might later overgrow and cause a symptomatic infection. An October 1997 study published in "Genitourinary Medicine" reported that 16 percent of men studied had yeast colonization of their penis. The rate was similar between heterosexual and homosexual men and the majority of these men had no symptoms. So it is possible for sex between a man and a woman to introduce yeast from the man's penis into the woman's vagina. But again, yeast introduced into the vagina does not necessarily mean a symptomatic infection will develop.
Frequent Sex Unlikely to Influence Yeast Infections
Women and the medical community have long wondered whether the frequency of sexual activity influences the risk for vaginal yeast infections. A study published in November 2000 in the "Journal of Women's Health and Gender-Based Medicine" examined whether there was an association between the frequency of sex and the frequency of vaginal yeast infections. The researchers found no increase in symptomatic yeast infections based on the frequency of sexual activity. A few earlier studies suggested that more sex might lead to more vaginal yeast infections, but the more recent "Journal of Women's Health and Gender-Based Medicine" study, which included 248 women, was clear in its declaration that there is no association. Notably, CDC does not list frequent sexual activity as a risk factor for vaginal yeast infections.
Receiving Oral Sex Might Lead to More Yeast Infections
A study published in February 2004 in "Sexually Transmitted Infections" found that receiving oral sex increased the likelihood of having a vaginal yeast infection. The article in the November 2000 issue of the "Journal of Women's Health and Gender-Based Medicine" noted the same finding. The association may be due to direct transmission of yeast from the mouth of the person giving the oral sex to the vagina of the person receiving oral sex -- as roughly 30 percent of healthy people have Candida albicans in their mouth. Another possible explanation might be the development of a mild abrasion of the vaginal mucosa during oral sex, giving yeast present in the vagina an opportunity to overgrow. As previously noted, the vaginal environment is delicately balanced and the introduction of any foreign substance -- including those in saliva -- may be enough to throw off that balance.
Usually Gone in Days
Fortunately, 80 to 90 percent of vaginal yeast infections that are diagnosed because of itching, pain and discharge are easily and quickly treated, with resolution of symptoms in 3 days or less. Topical over-the-counter and prescription antifungal products that are applied to the vagina and vulva for 1 to 3 days work well for most women. The remaining 10 to 20 percent of infections are more difficult to treat. This can be due to an infection that persists despite using a topical antifungal medication, which most often occurs because a type of yeast other than Candida albicans is causing the infection. Recurrent infections, defined as 4 or more symptomatic yeast infections within 1 year, can also be more difficult to treat. Some vaginal yeast infections present with severe symptoms, and some woman have a disease such as HIV that makes treatment more challenging and requires a longer course of medication.
Warnings and Precautions
Sexually transmitted diseases are common and have potentially significant health impacts. Any change in vaginal discharge, pain with sex or unexpected vaginal bleeding should prompt a visit to your healthcare provider. See your provider as soon as possible and before you have sex again to avoid potential spread of a sexually transmitted disease. Your provider can perform testing, make a diagnosis and provide any necessary treatment.
Pregnancy is a time when yeast infections are particularly common and the types of medications used are important. Any vaginal symptoms during pregnancy, including itching, pain, bleeding or change in discharge, should be evaluated immediately by your healthcare provider.
Reviewed by: Tina M. St. John, M.D.