Bacterial Vaginosis (BV) is a common vaginal condition caused by an imbalance in the natural bacterial environment. This occurs when protective, acid-producing bacteria are reduced, allowing an overgrowth of other bacteria. BV often results in symptoms such as a thin, grayish discharge and a distinct “fishy” odor. Antibiotics are the standard treatment prescribed to correct this bacterial overgrowth. Many people worry the medication might worsen their symptoms, confusing temporary side effects with a failure to cure the infection.
Understanding BV Treatment Mechanisms
The goal of antibiotic therapy for BV is to suppress the high concentration of overgrown anaerobic bacteria, such as Gardnerella vaginalis. These bacteria thrive when the vaginal pH rises above its normal acidic level. Medications like metronidazole and clindamycin specifically target and reduce the population of these anaerobic organisms.
By eliminating the excessive anaerobic bacteria, the treatment allows beneficial bacteria, primarily Lactobacilli species, to repopulate. Lactobacilli produce lactic acid, which restores the protective acidic pH of the vagina. When treatment is successful, symptoms begin to improve within a few days. It is important to complete the full course of medication, even if symptoms disappear early, to prevent the infection from returning.
Why Symptoms May Seem Worse During Treatment
The perception that symptoms are worsening while on antibiotics is often due to the medication’s side effects, not a progression of the BV itself. Oral metronidazole, a common BV treatment, is associated with gastrointestinal upset, including nausea, vomiting, or diarrhea. This drug can also cause a metallic taste in the mouth.
If a topical gel or cream formulation is used, localized irritation, mild burning, or itching can occur temporarily at the application site. These physical reactions are related to how the body processes the medication and are usually temporary. These common side effects should not be mistaken for the underlying BV infection becoming more severe.
The Risk of Post-Treatment Secondary Infections
A reason symptoms may change or appear worse after the antibiotic course is complete is the disruption of the vaginal microbiome. Antibiotics are broad-acting and do not selectively kill only the BV-causing bacteria; they also reduce the levels of protective Lactobacilli. This widespread bacterial elimination creates an environment susceptible to other infections.
The most common secondary infection is Vulvovaginal Candidiasis, or a yeast infection. This occurs when the fungus Candida albicans overgrows in the antibiotic-altered environment. Symptoms of a yeast infection—intense itching, burning, and a thick, cottage cheese-like discharge—are distinct from BV.
Another frequent issue is the rapid recurrence of BV, which happens in up to 50% of people within 12 months after treatment. Recurrence occurs when the Lactobacilli fail to fully repopulate and restore the acidic balance. This allows the original anaerobic bacteria to quickly re-establish themselves, causing symptoms to return soon after the antibiotic is finished.
When to Contact a Healthcare Provider
It is important to differentiate between typical antibiotic side effects and signs that require medical reevaluation. You should contact a healthcare provider if you experience symptoms suggesting a severe allergic reaction, such as difficulty breathing, swelling of the face or throat, or a widespread rash. These reactions are rare but require immediate attention.
Seek medical advice if your initial BV symptoms have not improved or have worsened within a few days of completing the antibiotic course. A provider should also be contacted if new symptoms appear, such as significant vaginal itching and a thick, odorless discharge, suggesting a secondary yeast infection. Persistent or returning symptoms indicate the need for further testing to rule out treatment failure, recurrence, or an alternative diagnosis.