The Vagina Has “Good Bacteria” Too: Why Is Lactobacillus So Important?
February 13, 2026, Fertility Classroom
In the clinic, many women actually have similar concerns:
Repeated abnormal discharge
Frequent infections and repeated medication use
Feeling that something is still not quite right, even with careful hygiene
Many times, the issue is not necessarily whether there are “bad bacteria,” but that the good bacteria that should originally be there have decreased.
What does a normal vaginal microbiome look like?
In a healthy woman’s vagina, 70–90% of the microbiome consists of Lactobacillus.
The most common and important types include:
• L. crispatus
• L. gasseri
• L. jensenii
• L. iners
These Lactobacillus species do three very important things:
- Convert glycogen into lactic acid
→ This helps maintain the vagina at an acidic pH of 4.0–4.5 - Inhibit the growth of harmful bacteria
→ Such as bacteria associated with bacterial vaginosis - Produce antimicrobial substances
→ Including hydrogen peroxide and bacteriocins, which help strengthen the defense of the vaginal mucosa
When Lactobacillus is present, the vagina has protective power.
Why does the vaginal microbiome become imbalanced?
The vaginal microbiome is actually very sensitive and can be affected by many factors, including:
• Menstrual cycle
• Pregnancy and postpartum changes
• Menopause and hormonal decline
• Antibiotic use
• Sexual activity
• Excessive cleansing or douching
• Differences in contraceptive methods
When Lactobacillus decreases, anaerobic bacteria such as Gardnerella, Atopobium, and Prevotella can increase more easily.
At this point, the microbiome may become “more diverse,” but it is actually an unhealthy kind of diversity.
This condition is called:
Vaginal microbiome imbalance, or dysbiosis.
The key is not to wash away the bad bacteria, but to preserve the good bacteria.
When Lactobacillus remains stable, the vagina naturally has protection. Once good bacteria become insufficient, repeated discomfort and infections are more likely to occur.
Yun-I wishes your dreams come true!
