What is the difference between bacterial vaginosis and yeast infection?

Bacterial vaginosis (BV) and vulvovaginal candidiasis (commonly referred to as a “yeast infection”) are two distinct, common causes of vaginal discomfort—but they differ significantly in etiology, clinical presentation, diagnostic criteria, and treatment.

Bacterial vaginosis results from a disruption in the normal vaginal microbiota, characterized by a reduction in protective hydrogen-peroxide–producing Lactobacillus species and an overgrowth of anaerobic bacteria such as Gardnerella vaginalis, Prevotella, Mobiluncus, and Atopobium vaginae. Clinically, BV typically presents with a thin, grayish-white vaginal discharge that has a characteristic “fishy” odor—often intensified after intercourse or during menses. Pruritus (itching) and vulvar irritation are usually mild or absent. Diagnosis is commonly confirmed using Amsel’s criteria (≥3 of: homogeneous discharge, pH >4.5, positive “whiff test,” and presence of clue cells on saline wet mount) or nucleic acid amplification tests (NAATs) targeting key bacterial markers.

In contrast, vulvovaginal candidiasis is most often caused by Candida albicans (though non-albicans species like C. glabrata are increasingly implicated, especially in recurrent or treatment-resistant cases). It is characterized by intense pruritus, vulvar erythema, swelling, and a thick, white, “cottage cheese–like” discharge. Unlike BV, vaginal pH is typically normal (≤4.5), and there is no fishy odor. Diagnosis relies on clinical assessment supported by potassium hydroxide (KOH) microscopy demonstrating hyphae or budding yeast, or fungal culture when needed—particularly for suspected non-albicans infections.

Treatment strategies reflect these pathophysiological differences: BV is managed with antimicrobials active against anaerobes—such as oral metronidazole, topical metronidazole gel, or clindamycin cream. Yeast infections are treated with antifungal agents—including topical azoles (e.g., clotrimazole, miconazole) or oral fluconazole. Accurate diagnosis is essential, as misdiagnosis and inappropriate therapy can lead to symptom persistence, recurrence, and unnecessary side effects.