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.

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Candida albicans affecting the nails
 DermNet / CC BY-NC-ND

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.

This photo contains content that some people may find graphic or disturbing.

Candida albicans folliculitis
 DermNet / CC BY-NC-ND

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 the risk of vaginal candidiasis but that it is not "passed" from sexual partners to the vagina as some had believed.

Interestingly, while oral sex and masturbation with saliva were found to be risk factors for vaginal candidiasis, a yeast infection could develop whether the oral sex 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 a person with vaginal candidiasis could transmit thrush or penile yeast infections to their sexual partners.

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 vaginal yeast infections. In fact, one type known as Candida glabrata occurred more frequently than even C. albicans.

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

Complications

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 people with vaginal 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 person can get if their immune status is poor.

A Word From Verywell

Most people do not need to be concerned about the sexual transmission of thrush or yeast infections. However, people who have 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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