Vaginal yeast infection (also called vulvovaginal candidiasis or moniliasis) is a common fungal infection of the vagina and vulva caused primarily by overgrowth of Candida albicans (or occasionally other Candida species), a yeast normally present in small amounts in the vagina, mouth, gut, and skin. Overgrowth occurs when the natural balance of vaginal bacteria and yeast is disrupted, allowing Candida to multiply excessively. Common triggers include antibiotic use (which kills protective lactobacilli), hormonal changes (pregnancy, birth control pills, hormone therapy, menstrual cycle), high blood sugar (diabetes or prediabetes), weakened immune system (e.g., from HIV, corticosteroids, chemotherapy), increased estrogen levels, tight/synthetic underwear or wet clothing promoting moisture, douching, or sexual activity (though not classified as an STI). Symptoms typically include intense vaginal and vulvar itching (often the most prominent), thick white vaginal discharge resembling cottage cheese (usually odorless or mildly yeasty), redness, swelling, and irritation of the vulva, burning sensation during urination or sex (dyspareunia), soreness or raw feeling, and sometimes small fissures or cracks in the vulvar skin from scratching. It affects up to 75% of women at least once, with recurrent infections (4+ episodes per year) occurring in a smaller subset.