Is Thrush Contagious?

Oral thrush (oral candidiasis) and vaginal yeast infections (vaginal candidiasis) are both usually caused by an overgrowth of a fungus known as Candida albicans that lives naturally in our bodies. Both oral thrush and yeast infections cause creamy white lesions that can bleed if rubbed or scraped.

Because thrush can affect both the mouth and the vagina, many people assume that the fungus can be passed through oral sex. However, it isn't spread this way. There is an association between oral sex and candidiasis, but the risk isn't linked to the transmission of the fungus.

This article looks at the causes and risk factors of candidiasis and explains how oral sex can trigger yeast infection in some people. It also describes the complications of candidiasis and things you can do to reduce the risk.

Causes of Candidiasis

C. albicans is part of our body's natural flora, microorganisms like fungi and bacteria that live on and in our bodies. Under normal conditions, these organisms are controlled and don't cause problems so long as our immune systems are healthy.

When C. albicans is allowed to overgrow, candidiasis is the result. The infection is considered opportunistic in that it only occurs when the immune system fails to control the fungus. Changes in the vaginal environment can also cause C. albicans to overgrow.

Risk factors for candidiasis include:

• Changes in vaginal acidity
• Changes in vaginal flora
• An immune-suppressive disorder like HIV
• Immunosuppressive drugs like steroids
• Babies and infants under 1 year
• Wearing dentures
• Diabetes
• Cancer
• Taking medications that cause dry mouth
• Smoking

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Though candidiasis is normally associated with oral thrush and vaginal yeast infections, it can also affect the penis, skin, nails, esophagus (the tube that goes from the throat to the stomach), and lungs. The fungus can also spread (disseminate) through the bloodstream and affect the heart, brain, eyes, bones, and other parts of the body.

The severity of candidiasis is directly related to how suppressed your immune system is. Advanced HIV infection is one of the conditions linked to the risk of invasive candidiasis (candidiasis that spreads).

Is Thrush Contagious?

C. albicans lives naturally in our bodies. It doesn't typically require transmission from another person. However, certain behaviors and conditions have been linked to an increased risk of an overgrowth of C. albicans, which is what leads to candidiasis.

Oral Thrush

There is no evidence that a vaginal yeast infection or penile yeast infection can be passed to someone performing oral sex. Researchers from Brazil found that oral candidiasis was not so much linked to sexual behaviors but rather to underlying immune disorders like HIV.

People who are immunocompromised or taking immunosuppressant drugs (like corticosteroids) are vulnerable to oral thrush. Inhaled corticosteroids used to treat asthma are a relatively common cause. If you're taking antibiotics to treat a bacterial infection, the medicine can also kill the natural bacteria in your body that help keep C. albicans in check.

Vaginal Candidiasis

There is evidence that cunnilingus (oral-vaginal sex) can trigger vaginal yeast infections. The reason for this isn't clear. One theory proposed by a single case study is that saliva introduced into the vagina can alter the concentration of "helpful" bacteria called lactobacillus.

Lactobacilli are naturally found in the vagina and digestive tract and, among other things, help control C. albicans. Enzymes in saliva can neutralize this bacteria, allowing C. albicans to grow beyond their normal limits.

This doesn't mean that receiving cunnilingus "causes" a yeast infection. It simply increases the risk that C. albicans could grow out of control. Other things that can affect your natural vaginal flora include vaginal douching and frequent vaginal sex. Condomless vaginal sex also poses a risk in that it can cause bacterial dysbiosis (the imbalance of bacteria) up to a week afterward.

Candidiasis is not a sexually transmitted infection (STI) and is not associated with having multiple sexual partners, or a new partner.

Complications

Thrush—both oral and vaginal—creates lesions that can crack and bleed. So even though candidiasis is not spread by sex, it can create an environment that could make it easier to catch other infections, including HIV.

In fact, research has shown that people assigned female at birth who had persistent or recurrent yeast infections were more likely to get HIV than those who didn't.

An active yeast infection causes inflammation that attracts immune-fighting cells, called CD4 T-cells, to the site of the infection. These are the very cells that HIV targets for infection. As such, having a yeast infection increases the potential for an HIV infection.

Public health authorities, including Planned Parenthood, advise people with vaginal yeast infections to avoid sex until the infection clears.

Prevention

Because oral sex can trigger or worsen a vaginal yeast infection, it is important to practice safer sex if you are prone to recurrence. This includes using a dental dam when engaging in cunnilingus. Dental dams can be found online and in most drugstores.

Also, consider using a water-based lubricant instead of saliva for mutual masturbation or vaginal sex. Some water-based lubricants, like KY Jelly, do not affect vaginal lactobacilli, while others, like Replens Silky Soft, may promote lactobacillus growth.

If you have a yeast infection, you should either avoid sex or use external condoms or internal condoms during sex. Doing so decreases the risk of HIV and other STIs.

Summary

Oral thrush and vaginal yeast infections are both usually caused by the overgrowth of the fungus Candida albicans. These conditions, known as oral or vaginal candidiasis, are caused when the immune system is unable to control the naturally occurring fungus. It can also occur when the natural environment of the vagina is disrupted.

Candidiasis is not an STI and cannot be passed through oral sex. With that said, oral sex can increase the risk of a yeast infection by causing an imbalance in vaginal flora. Enzymes in saliva appear to neutralize "helpful" bacteria that would otherwise control Candida albicans.

Vaginal sex is not advised if you have a yeast infection as the infection can compromise vaginal tissues and increase the risk of HIV. If you do have sex, use condoms. Dental dams should also be used if you have a yeast infection to avoid making the infection worse.

A Word From Verywell

If you have recurrent vaginal yeast infections, speak with your healthcare provider about ways to reduce the incidence or severity of outbreaks. This may include practicing safer sex, starting an anti-Candida diet, or eating probiotic foods or supplements that help maintain the natural vaginal flora.

People who are severely immunocompromised may need to take daily prophylactic (preventive) anti-fungal drugs to avoid infection.

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