What Is a Vaginal Yeast Infection? Causes and Symptoms

A vaginal yeast infection, clinically called vulvovaginal candidiasis, is an overgrowth of Candida fungus in the vagina and surrounding tissue. The organism responsible, usually Candida albicans, already lives on the vaginal lining of most healthy people without causing trouble. Roughly three in four women experience at least one symptomatic episode during their reproductive years, making this one of the most common reasons for a gynecology visit. But what actually tips the balance from harmless colonization to itching and discharge involves more moving parts than most people realize.

The Fungus Behind the Infection

Candida albicans is not an invader you catch from the outside world. It colonizes the gut, mouth, and vaginal mucosa of most humans from an early age and coexists peacefully with the body’s other microorganisms most of the time.1Oxford Academic. Vaginal Candida albicans infections: host–pathogen–microbiome interactions The trouble starts when conditions shift in a way that lets Candida outcompete its neighbors or change its own behavior. When it senses the right cues, C. albicans can switch from a round yeast form to an elongated hyphal form, and those thread-like hyphae are far better at burrowing into the surface layer of vaginal cells and causing damage.2PLoS ONE. Fungal burden, dimorphic transition and candidalysin: Role in Candida albicans-induced vaginal cell damage and mitochondrial activation in vitro The fungus also produces a toxin called candidalysin that injures tissue and triggers the immune system’s alarm signals. Research in animal models shows that hyphal growth and candidalysin production together are the dominant drivers of tissue damage and immune activation during mucosal Candida infections.3PubMed Central. The combinatorial action of hyphal growth and candidalysin is critical for promoting Candida albicans oropharyngeal infection

C. albicans is the culprit in most cases, but non-albicans Candida species account for roughly 10% to as high as 45% of infections in some populations.4PubMed Central. An Update on the Roles of Non-albicans Candida Species in Vulvovaginitis Candida glabrata is the most common of these. Infections caused by non-albicans species tend to be milder in presentation but more stubborn, often recurring and resisting the standard antifungal treatments that work well against C. albicans.5PubMed. Vulvovaginal Candidiasis Caused by Non-albicans Candida Species: New Insights This matters because a woman who keeps getting symptoms despite treatment may be dealing with a different species altogether, something a standard over-the-counter antifungal cannot address.

Why It Happens

One of the biggest protective factors in the vagina is Lactobacillus bacteria. These friendly bacteria produce lactic acid and hydrogen peroxide, keeping the pH low enough to hold Candida in check. Laboratory studies show that several Lactobacillus strains significantly reduce C. albicans’s ability to stick to vaginal cells through a combination of competitive exclusion and the acids they release.6PLoS ONE. Isolation of Vaginal Lactobacilli and Characterization of Anti-Candida Activity Research further confirms that the anti-Candida effect of Lactobacillus supernatants comes largely from organic acids, with hydrogen peroxide playing an additional supporting role.7FEMS Yeast Research. Anti-Candida activity of beneficial vaginal lactobacilli in in vitro assays and in a murine experimental model Anything that depletes these Lactobacillus populations or otherwise disrupts the vaginal environment can open the door for Candida to grow unchecked.

Several common situations create that opening:

Vaginal Douching and Infection Risk

Douching is widely discouraged by health authorities, and the evidence on yeast infections gives specific reasons why. A study of Cambodian women found that douching was significantly associated with vaginal candidiasis even after controlling for sociodemographic factors and other genital symptoms.11Journal of Epidemiology. Vaginal Douching in Cambodian Women: Its Prevalence and Association With Vaginal Candidiasis Interestingly, the same study found no link between douching and either trichomoniasis or bacterial vaginosis, suggesting the mechanism may be specific to how douching affects the Candida-Lactobacillus balance.

Research also shows that while many douching solutions can inhibit yeast growth in a lab dish, using them regularly in practice may still increase the risk of infection because they disrupt the protective bacterial community.12Iraqi Journal of Biotechnology. Isolation of Candida spp. from Women with Yeast Vaginitis and Study the Effect of Different Types of Douching on Candida spp. Frequent douching also appears to increase the likelihood of non-albicans Candida species, which are harder to treat.13Medical Mycology. Does vaginal douching affect the type of candidal vulvovaginal infection? The paradox is clear: cleaning out the vagina with solutions feels hygienic but can actually make yeast infections more likely and more resistant to standard treatment.

What the Symptoms Actually Look Like

The classic description of a yeast infection involves itching, a thick white “cottage cheese” discharge, and redness or soreness of the vulva and vaginal opening. But the clinical picture is not as neat as textbooks suggest. A study that looked at the relationship between the number of Candida organisms in the vagina and specific symptoms found that only itching (pruritus) and objectively assessed abnormal discharge were statistically reliable indicators of an actual Candida infection. Other symptoms that women commonly attribute to yeast infections, including their own subjective sense of abnormal discharge, did not correlate with laboratory-confirmed fungal growth.14PubMed. Candida concentrations in the vagina and their association with signs and symptoms of vaginal candidosis

In practical terms, this means itching is the strongest clue. The discharge, when present, tends to be white, thick, and relatively odorless, which helps distinguish it from the thin, gray, fishy-smelling discharge of bacterial vaginosis. Some women also experience burning during urination or discomfort during intercourse. Redness and swelling of the vulva are common but not universal.

Why Self-Diagnosis Gets It Wrong So Often

Here is where most people run into trouble. Vulvar itching is a common complaint, and many women assume it means a yeast infection and reach for an over-the-counter antifungal. The problem is that itching has a long list of other causes. Atopic dermatitis, irritant contact dermatitis, and allergic contact dermatitis are extremely common noninfectious causes of vulvar itch that are frequently misdiagnosed, even by clinicians who are not dermatologists.15PubMed. Atopic and Contact Dermatitis of the Vulva Think of all the potential irritants that contact vulvar skin: soaps, detergents, panty liners, synthetic fabrics, scented hygiene products. Any of these can trigger itching and redness that look and feel like a yeast infection but will not respond to antifungal treatment.

Bacterial vaginosis and trichomoniasis can also overlap with yeast infection symptoms. Among postmenopausal women attending a vaginitis clinic, only about a third could be given a definitive diagnosis of bacterial vaginosis, Candida, or Trichomonas infection. The remaining two thirds of symptomatic women had no microbiologic diagnosis at all, and alternative causes like estrogen deficiency, noninfectious irritation, or skin conditions had to be considered.16PubMed. The relationship of bacterial vaginosis, Candida and Trichomonas infection to symptomatic vaginitis in postmenopausal women attending a vaginitis clinic That statistic is a good reason to get a proper diagnosis rather than self-treating repeatedly. Misusing antifungals can mask the real cause of symptoms and contribute to antifungal resistance.

The Gut Reservoir Question

For decades, the prevailing idea was that recurrent yeast infections trace back to a reservoir of Candida in the gut. A classic study from the late 1970s found that if C. albicans was cultured from the vagina, it was always also found in the stool, and if it was absent from the stool, it was never found in the vagina.17PubMed. Recurrent vaginal candidiasis. Importance of an intestinal reservoir The implication was that the gut continuously reseeds the vagina, making a lasting cure impossible without eliminating the fungus from the digestive tract first.

More recent research complicates this picture. A pilot study examining the fungal and bacterial microbiomes of both vaginal and gastrointestinal sites in women with recurrent infections found that Candida species pairings between the two sites were uncommon, suggesting the gut reservoir may not be the main driver of recurrent symptoms for most women.18PubMed Central. The impact of fluconazole use on the fungal and bacterial microbiomes in recurrent Vulvovaginal Candidiasis (RVVC): a pilot study of vaginal and gastrointestinal site interplay This is still an active area of investigation. The gut almost certainly harbors Candida in most people, but whether and how often it directly recolonizes the vagina after treatment remains debated. What does seem clear is that recurrence is not simply a matter of re-infection from a single source. Host immune factors, genetic susceptibility, and the vaginal microbiome all play roles.

What Makes Some Women Get Repeated Infections

Between 5% and 9% of women experience recurrent vulvovaginal candidiasis, defined as four or more symptomatic episodes per year.1Oxford Academic. Vaginal Candida albicans infections: host–pathogen–microbiome interactions For these women, the experience is genuinely disruptive to daily life, and the causes go beyond the usual risk factors like antibiotics or high estrogen.

The immune system’s response to Candida is a major piece of the puzzle. The body relies on a specific branch of immune defense involving Th17 cells to keep mucosal Candida in check.19PubMed Central. Host responses to Candida albicans: Th17 cells and mucosal candidiasis When the recognition pathways that sense the fungus and trigger those Th17 responses are impaired, mucosal defenses weaken.20PubMed Central. Th17 cells in immunity to Candida albicans Genetic variation in immune system genes has been linked to increased susceptibility to both recurrent vaginal infections and other forms of candidiasis.21PubMed Central. Genetic susceptibility to Candida infections This means some women are simply dealt an immune hand that makes them more vulnerable, no matter how careful they are about the lifestyle factors commonly cited in prevention advice.

Is It Sexually Transmitted?

Yeast infections are not classified as sexually transmitted infections, but the relationship between sexual activity and recurrence is more nuanced than a flat “no.” In a study that followed 148 women for a year after an initial episode, culturing Candida from a male partner’s mouth, stool, urine, or semen did not predict whether the woman would have a recurrence. However, certain sexual behaviors were associated with repeat episodes: women who reported cunnilingus or masturbation with saliva had roughly two to three times the risk of recurrence.22PubMed. Candida transmission and sexual behaviors as risks for a repeat episode of Candida vulvovaginitis The likely explanation is that saliva introduces oral Candida or other microbes that disturb the vaginal environment, rather than the partner acting as a persistent reservoir.

An older study looking at matched couples found that both partners had genital yeast in 21 of 50 couples studied, which does suggest some degree of sexual exchange.23Sexually Transmitted Infections. How often are gonorrhoea and genital yeast infection sexually transmitted? Still, the general consensus remains that most yeast infections arise from the woman’s own Candida population shifting out of balance, not from transmission by a partner. Treating male partners routinely has not been shown to reduce recurrence in women.

Yeast Infections During Pregnancy

Pregnancy creates a near-perfect storm for vaginal candidiasis. Estrogen and progesterone levels climb, glycogen deposition in vaginal tissue increases, local immune responses shift to protect the fetus, and vaginal pH drops. Candida colonization rates rise to around 30% during pregnancy as measured by culture, with the highest rates in the third trimester.24PubMed Central. Prevalence and Risk Factors of Vulvovaginal Candidosis during Pregnancy: A Review The concern goes beyond discomfort: emerging evidence links vaginal candidiasis in pregnancy to complications including preterm labor, premature rupture of membranes, and chorioamnionitis.24PubMed Central. Prevalence and Risk Factors of Vulvovaginal Candidosis during Pregnancy: A Review Treatment options during pregnancy are more limited because oral antifungals like fluconazole carry potential risks to the fetus, so topical azole creams are generally preferred.

When Yeast Infections Leave a Mark

Most yeast infections clear up within a week or two of treatment and leave no lasting effects. But there is an underappreciated consequence that can follow repeated infections. In a mouse model, researchers found that animals subjected to recurrent Candida infections developed persistent mechanical allodynia localized to the vulva, essentially ongoing pain sensitivity that lasted at least three weeks after the infection itself had resolved. The affected tissue showed hyperinnervation, meaning an increased density of pain-signaling nerve fibers in the vaginal lining.25PubMed Central. Repeated vulvovaginal fungal infections cause persistent pain in a mouse model of vulvodynia Long-lasting pain occurred even after a single extended Candida infection, not just repeated ones. This finding has implications for vulvodynia, a chronic pain condition that many women struggle to get diagnosed. It suggests that for some women, a history of recurrent yeast infections may physically rewire the nerve supply in vulvar tissue, leaving behind pain that persists long after the fungus is gone. If you have chronic vulvar pain that started around the time of yeast infections, this is worth discussing with a clinician rather than assuming the pain is “just another yeast infection.”