"I manage it the same way, so why do I keep getting recurrent vaginitis?" In the clinic, even when hygiene habits are similar and treatment is followed well, one or two people in particular have the same symptoms repeat. Until now this was often passed off vaguely with the word "constitution," but recent microbiome studies show that a considerable part of that "constitution" may actually arise from an inborn genetic tendency and from immune·metabolic state. Today I will organize why individual differences arise in the distribution of vaginal lactic-acid bacteria (microbiome), and what role genetics and environment each play.
The vaginal microbiome is not one single form
Just because it is a healthy vaginal environment does not mean everyone has the same bacterial composition. In the 2011 report by Ravel et al., which became the starting point of vaginal microbiome research, the vaginal bacterial communities of asymptomatic women of reproductive age could be broadly divided into five types. This typology is commonly called Community State Type.
Four of the types were each environments dominated by a different kind of lactic-acid bacterium, and the remaining one type was an environment with few lactic-acid bacteria and a high proportion of anaerobic bacteria. This means that even when it looks like the same "healthy" state, which lactic-acid bacterium leads differs from person to person.
- When lactic-acid bacteria are abundant, they make lactic acid to keep the inside of the vagina acidic, and this plays the role of a protective barrier that suppresses the overgrowth of stray bacteria.
- Even among the same lactic-acid bacteria, differences in stability are reported depending on the kind. One species is associated with a relatively stable protective environment, while another common species is frequently observed in both the healthy state and the disturbed state, so its role is not simple.
So it is not "if there are just a lot of lactic-acid bacteria, that's it"; rather, which bacteria are established in what proportion is the more important picture.
Why bacterial distribution differs from person to person even in the same environment
The vaginal ecosystem is greatly affected by the environment. The bacterial composition changes noticeably according to menopausal status, whether bacterial vaginosis accompanies it, and hormonal state. Yet the interesting point is that even after accounting for those environmental factors, individual differences remain from person to person.
A twin cohort study targeting Korean women (Si et al., 2017) looked at part of this individual difference through the lens of "genetics." Analyzing identical·fraternal twins together allows one to estimate how much a trait carries a genetic tendency, and in this study, the genetic influence appeared relatively large in the relative proportion of beneficial lactic-acid bacteria and certain bacteria known as problem bacteria.
In other words, the vaginal microbiome is an area in which the environment's share—"how I manage it"—and genetics' share—"what tendency I was born with"—act together.
A separate study targeting European women also reported a result that there is a genetic tendency in the distribution of representative protective lactic-acid bacteria, suggesting the possibility that such individual differences are not a phenomenon limited to a specific population group. However, it is that genetics influences the "proportion," not that it determines the outcome.
The link between immune genes and bacterial composition
Immune-related genes are pointed to as one of the channels through which genetics influences the microbiome. In the aforementioned Korean twin study, a signal was observed in which a genetic variant related to interleukin-5 (IL5) was associated with an increase in bacteria classified as problem bacteria.
Interleukin-5 is one of the immune signaling substances involved in allergic·parasitic reactions and so on, connected to one axis of the mucosal immune response. This result supports the hypothesis that "the inborn tendency of the immune response can influence which bacteria become well established on the vaginal mucosa."
In the clinic, among those struggling with recurrent vaginitis, it is not uncommon for someone to blame themselves, saying "shouldn't I be doing hygiene even more thoroughly?" However, knowing that immune·genetic background is intertwined with bacterial composition makes it easier to understand that, rather than excessive management of the unconditional wash-more-and-wipe-more kind, an approach that stabilizes the mucosal environment itself is reasonable. Frequent cleansing or excessive vaginal douching can rather reduce protective lactic-acid bacteria and disturb the balance.
Obesity·metabolic state and the vaginal microbiome
The microbiome does not move independently inside the vagina alone. The same Korean twin study also observed an association signal between obesity indicators and changes in the vaginal microbiome. In obese women, a change in bacterial diversity and problem-bacteria-related changes were seen together.
In recent medicine, obesity is often understood not as a simple weight problem but as a chronic low-grade inflammatory state. It is a natural interpretation that such a systemic metabolic·inflammatory state can affect mucosal immunity and microbial balance. The point that the gut microbiome interacts with systemic metabolism has already been broadly dealt with, and the vaginal microbiome too can be connected to the systemic state in a similar context.
Clinically, this carries the following meaning.
- Systemic management such as weight·blood glucose·sleep·stress is not unrelated to vaginal health.
- Rather than viewing recurring vaginal discomfort only as a local problem, checking metabolic·lifestyle factors together can be helpful.
If it is a period when weight, hormones, and metabolic changes arrive all at once, reading the hormonal reasons why one gains weight more easily during menopause together also helps in understanding the big picture of systemic change.
Genetics·environment·hormones, how they work at a glance
If I organize the factors that influence the vaginal microbiome, they are as follows. The key point is that it is not determined by any one alone.
| Category | Representative factor | Characteristic | Room for management |
|---|---|---|---|
| Genetic tendency | Relative proportion of protective·problem bacteria, immune gene variants | Acts as an inborn "tendency" | Hard to change directly |
| Hormonal state | Menopause, menstrual cycle, estrogen change | Affects the mucosal environment and acidity | Adjustable through a medical visit |
| Environment·lifestyle | Antibiotics, douching, sexual activity, weight·eating habits | Shakes or restores the balance | Large adjustable area |
| Comorbid state | Bacterial vaginosis, metabolic abnormality, inflammation | Greatly changes bacterial composition | Improved through treatment·management |
As the table shows, genetics can make the starting line different, but it does not set the finish line. This is because an adjustable area clearly exists.
If recurrent vaginitis or changes in discharge concern you, checking the causes of recurring vaginitis together is the first step. Organizing the symptom pattern and lifestyle together in advance makes consultation much smoother.
반복되는 질 불편감, 채팅으로 먼저 상담하기Three frequently heard questions
I have gathered the questions that come up most when I explain this topic in the clinic.
Does being genetic mean there's nothing to be done
That is not so. Genetics is a "tendency," not a "fate." Environmental factors can be sufficiently corrected through lifestyle, hormonal state, local treatment when needed (e.g., low-dose vaginal estrogen or moisturizer), probiotic strategies, and so on. Even if the inborn tendency is unfavorable, there are many cases of regaining balance through management.
Why are obesity and vaginal health connected
The view of seeing obesity not only as a metabolic abnormality but as a chronic inflammatory state is increasing. This is because such a metabolic·inflammatory state can affect mucosal immunity and microbial balance. Management of weight·blood glucose·sleep·stress can help reduce the recurrence of vaginal discomfort.
Do I absolutely have to get a genetic test
In general practice it is not essential. However, when symptoms recur, as in recurrent bacterial vaginosis or chronic vaginitis, an integrated evaluation that looks at lifestyle·hormones·microbial state together is useful. Whether to test is best decided together at a medical visit, looking at symptoms and history.
If you feel that the environment changes around menopause and vaginitis becomes more frequent, the article dealing with the reasons post-menopausal vaginitis increases is also a reference.
In summary
There are clear individual differences in the distribution of vaginal lactic-acid bacteria, and into those differences, not only environment but also genetic tendency and immune·metabolic state act together. The Korean twin cohort study confirmed genetic influence in the proportion of protective lactic-acid bacteria and problem bacteria, and also reported association signals with immune genes and obesity.
That said, there is no need to go to the conclusion "I was born with it, so there's nothing to be done." Rather, it is closer to evidence showing why a personalized approach that looks at genetics·immunity·metabolism·hormones together is needed, instead of "the same treatment for everyone." If you are worn out by recurring symptoms, I recommend checking integratively before concluding the cause to be a single thing.
내 증상에 맞는 관리 방향 상담받기Written by: Lee Dong-hee Director · Obstetrics and Gynecology Specialist · View doctor profile
First published October 26, 2025 · Last reviewed May 30, 2026
References: Si J et al. Cell Host Microbe (2017), Ravel J et al. PNAS (2011), Korean Society of Obstetrics and Gynecology
This article is intended to provide general health information and does not replace individual diagnosis or treatment. If you have symptoms, please consult through a medical visit.