Bacterial vaginosis (BV) in women is caused by an imbalance in the natural vaginal bacteria. Normally, the vagina has a healthy balance dominated by lactobacilli, which maintain an acidic environment that prevents overgrowth of harmful bacteria. BV occurs when the number of lactobacilli decreases and other bacteria, such as Gardnerella vaginalis and anaerobic bacteria, increase excessively

. Several factors can disrupt this balance and increase the risk of BV:

• Sexual activity, especially having new or multiple sex partners, or female sex partners, which may alter vaginal bacterial balance

• Use of an intrauterine device (IUD), particularly with irregular bleeding

• Douching, use of vaginal deodorants, scented soaps, bubble baths, and perfumed products that disturb vaginal flora and acidity

• Smoking, which is linked to higher BV risk

• Hormonal changes during puberty, pregnancy, or menopause that affect vaginal acidity

• Recent antibiotic use that kills beneficial bacteria, allowing overgrowth of harmful bacteria

• Stress and poor diet may also contribute by weakening immune defenses and affecting bacterial balance

• Certain demographic factors, such as being a Black woman, are associated with higher BV risk, possibly due to physiological stress and bacterial differences

BV is not classified as a sexually transmitted infection, though sexual activity influences its likelihood, and it can be transmitted between female partners

. It can also occur in women who have never had sex

. In summary, BV results from a shift in vaginal bacterial balance caused by factors that disrupt the protective lactobacilli and increase harmful bacteria growth. Managing risk factors such as sexual practices, hygiene habits, smoking, and hormonal influences can help reduce the chance of developing BV.