Yeast infections are not typically transmitted from person to person. They develop when Candida, a fungus that already lives on and inside your body, grows out of control. About 75% of women will experience at least one vaginal yeast infection in their lifetime, and the vast majority of those cases originate from their own body rather than from contact with someone else.
That said, there are specific situations where Candida can pass between people or relocate within your own body. Understanding these routes helps explain why yeast infections seem to appear out of nowhere and why they sometimes keep coming back.
Most Yeast Infections Start Inside Your Own Body
Candida species naturally live in your gut, mouth, and vaginal tract without causing any problems. They’re kept in check by beneficial bacteria, especially Lactobacillus, and by your immune system. A yeast infection happens when something disrupts that balance and allows Candida to multiply beyond its usual numbers.
For vaginal yeast infections specifically, the most common source is your own gastrointestinal tract. Your gut is home to the same Candida species that cause vaginal infections, and the rectum and vagina share similar microbial communities. When Candida from the rectum migrates the short distance to the vaginal tract, it can colonize and overgrow, especially if the protective Lactobacillus population has been weakened. This rectum-to-vagina translocation is one of the most well-established pathways for vaginal yeast infections.
This is why yeast infections can seem to come from nowhere. You didn’t “catch” it. The fungus was already present, and something tipped the balance.
What Triggers Overgrowth
The triggers that let Candida overgrow are often more important than transmission itself. Antibiotics are one of the biggest culprits. Beta-lactam antibiotics (a broad class that includes penicillin and amoxicillin) are particularly well-known for triggering vaginal yeast infections because they kill off the protective bacteria that normally keep Candida in check. If you’ve ever developed a yeast infection right after finishing a course of antibiotics, this is why.
Other common triggers include hormonal shifts from pregnancy, birth control pills, or hormone therapy. High blood sugar gives Candida more fuel to grow, which is why people with diabetes are more prone to yeast infections. A weakened immune system, whether from illness, medication, or stress, also opens the door. Even wearing tight, non-breathable clothing can create the warm, moist environment Candida thrives in.
Sexual Transmission Is Uncommon but Possible
The CDC classifies uncomplicated vulvovaginal yeast infections as “not usually acquired through sexual intercourse,” and treatment guidelines do not recommend treating sexual partners. This is the key reason yeast infections are not categorized as sexually transmitted infections.
However, “not usually” is not “never.” Candida can be passed between partners during vaginal, oral, or anal sex. A person with a vaginal yeast infection can transfer Candida to a male partner, potentially causing irritation or a rash on the penis (penile candidiasis). Oral sex can transfer Candida between the mouth and genitals in either direction. These cases are relatively uncommon, and in most instances the receiving partner’s immune system handles the fungus without developing symptoms.
The practical takeaway: if you have a yeast infection, sex can be uncomfortable and may slightly increase the chance of passing Candida to a partner, but it’s not a primary mode of transmission.
Mother-to-Child Transmission
One of the clearest person-to-person transmission routes is from mother to baby. Newborns can pick up Candida while still in the uterus or, more commonly, during passage through the birth canal. This is why oral thrush, a white, patchy Candida infection in the mouth, is so common in newborns and young infants. The same fungus can also worsen diaper rash, producing a distinctive raised red border around irritated skin.
Breastfeeding creates another opportunity for back-and-forth transmission. A baby with oral thrush can pass Candida to the nipple, and an infected nipple can reinfect the baby’s mouth, creating a cycle that sometimes requires treating both mother and child simultaneously.
Shared Objects and Indirect Contact
Candida can survive on surfaces and objects, which means indirect transmission through shared items is technically possible, though not a major risk for most adults. The scenario where this matters most involves young children. If two kids are bathing together and one has a yeast infection, using the same washcloth or sponge on both children can transfer the fungus.
For adults, sharing damp towels, underwear, or sex toys could theoretically move Candida from one person to another. The risk is low in practical terms because most healthy adults already carry Candida and their immune systems prevent overgrowth. Still, basic hygiene practices like using your own towels and washing shared items between uses eliminate the possibility entirely.
Why Yeast Infections Keep Coming Back
Roughly 5 to 8% of women experience recurrent yeast infections, defined as four or more episodes per year. Because the primary source of Candida is your own body, particularly your gut, reinfection from your own microbial reservoir is the most likely explanation for repeat infections. Treating a vaginal yeast infection clears the overgrowth locally, but Candida in the gastrointestinal tract remains and can migrate again if conditions allow it.
Recurrent infections are more common in people with ongoing risk factors: uncontrolled blood sugar, frequent antibiotic use, or immune suppression. If your yeast infections keep returning, the issue is almost certainly about your body’s internal environment rather than repeated exposure from an outside source.