Oral Sex and Candidiasis

Oral thrush and vaginal yeast infections are both caused by a naturally occurring fungus known as Candida albicans. The conditions referred to respectively as oral candidiasis and vaginal candidiasis, occur when a breakdown of the immune system provides the fungus an opportunity to thrive. Both are characterized by the appearance of creamy white lesions that can bleed if rubbed or scraped.

Given that candidiasis involves both the mouth and vagina, it may seem reasonable to assume that the fungus can be "caught" or "passed" during oral sex. The evidence of this remains split, with some studies suggesting a risk in women but not men, while others conclude that the risk, if any, is negligible.

Causes of Candidiasis

Candidiasis is simply the overgrowth of the C. albicans fungus. The infection is considered opportunistic in that it only occurs when the usual controls are disrupted. This may include changes in vaginal acidity, a depletion of the immune response, or medications that suppress the immune system.

Although we most commonly associate candidiasis with thrush and yeast infections, it can also affect the skin, nails, esophagus, and lungs or disseminate through the bloodstream to affect the heart, brain, eyes, bones, and other parts of the body.

The severity of candidiasis is directly related to the severity of immune suppression. Advanced HIV infection is one such example when candidiasis can become systemic and invasive.

Transmission Risk

As a naturally occurring fungus, C. albicans is really not something you can "catch." Everyone has some amount of C. albicans on the body (albeit controlled by a healthy immune system). As such, it is not sexually transmitted or something that can be passed from mother to child during pregnancy.

As far back as 2003, researchers at the University of Michigan concluded that sexual behaviors may play a role in woman's risk of vaginal candidiasis but that it is not "passed" from male partners as some had believed.

Interestingly, while oral sex and masturbation with saliva were found to be risk factors for candidiasis in women, a yeast infection could develop whether the male partner had oral thrush or not. What this suggests is that the disruption of vaginal tissues (perhaps by enzymes in saliva that break down sugar) provided C. albicans the opportunity to grow.

The researchers also concluded there was no evidence that men can get thrush or penile yeast infections from female partners with candidiasis.

Non-C. Albicans Infections

This is not to suggest that other forms of Candida cannot establish infection in the mouth or vagina. This includes a severe strain called Candida auris that is rare in the United States but is becoming a serious health threat in the developing world.

According to a 2015 study in the Journal of Environmental and Public Health, non-C. albicans strains such as Candida dubliniensis, Candida tropicalis, and Candida krusei can also cause yeast infections in women. In fact, one type known as Candida glabrata occurred more frequently than even C. albicans.

With that being said, the development of the yeast infections was more closely to poor immune status than any other factor. This includes C. auris which is mainly transmitted in healthcare settings to immunocompromised patients.

Complications

Taken as a whole, the bulk of the current evidence suggests that sexual transmission does not play a major role in vaginal or oral yeast infections. Despite this, public health organizations, including Planned Parenthood, commonly advise women with yeast infections to hold off on receiving oral sex until the infection resolves.

This is due in part to the fact that candidiasis compromises vaginal tissues, providing a greater opportunity for infection (including bacterial and viral ones). Moreover, the inflammation caused by Candida will trigger a steep rise in the number of immune cells, called CD4 T-cells, which are the primary target for HIV.

This is evidenced by a 2003 study in the Journal of Women's Health in which women with persistent or recurrent yeast infections were more likely to seroconvert (become HIV-positive) than women who without.

Despite the findings, it is important to note that having a recurrent or persistent yeast infection infers a poor immune status. So, it is not entirely clear how much a yeast infection contributed to the seroconversion or if it was simply symptomatic of the many illnesses a woman can get if her immune status is poor.

A Word From Verywell

Most women do not need to be concerned about the sexual transmission of thrush or yeast infections. However, women who suffer from recurrent vaginal yeast infections may want to discuss the benefits of safer sex with their doctor. Doing so may reduce the likelihood of candidiasis and other more potentially serious diseases.

In addition, an anti-Candida diet may reduce your risk by removing the dietary sugars that the fungus feeds on. Probiotic foods and supplements may also contribute to improved vaginal health by helping maintain the natural vaginal flora.

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Article Sources

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  1. Richardson JP, Moyes DL. Adaptive immune responses to Candida albicans infection. Virulence. 2015;6(4):327-37. doi: 10.1080/21505594.2015.1004977

  2. Reed, B.; Zazove, P.; Pierson, C. et al. Candida transmission and sexual behaviors as risks for a repeat episode of Candida vulvovaginitis.J Womens Health (Larchmt). 2003 Dec;12(10):979-89. doi:10.1089/154099903322643901.

  3. Hester, R. and Kennedy, S. Candida infection as a risk factor for HIV transmission.J Womens Health (Larchmt). 2003 Jun;12(5):487-94. doi:10.1089/154099903766651612.

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