Your Vaginal Microbiome: Why It Matters and How to Keep It Healthy

The vaginal microbiome is one of the most fascinating and overlooked aspects of women's health. It is a delicate ecosystem of bacteria that plays a vital role in protecting you from infections, supporting fertility, and maintaining overall gynaecological wellbeing. Yet despite its importance, most women have never been told about it – and many of the products marketed to women actually do more harm than good.

As a gynaecologist, I regularly see patients with recurrent thrush, bacterial vaginosis, or unexplained irritation, and in many cases the root of the problem lies in a disrupted vaginal microbiome. I want to explain what this ecosystem is, how it works, and what the evidence actually says about keeping it healthy.

What is the vaginal microbiome?

The vaginal microbiome refers to the community of microorganisms – predominantly bacteria – that live in the vagina. In a healthy vaginal environment, the dominant bacteria are Lactobacillus species, particularly Lactobacillus crispatus, L. iners, L. gasseri, and L. jensenii. These beneficial bacteria are not simply passive residents; they are active guardians of your vaginal health.

Lactobacilli perform several critical functions:

• Produce lactic acid, which maintains the vaginal pH between 3.8 and 4.5 – an acidic environment that inhibits the growth of harmful bacteria and pathogens
• Generate hydrogen peroxide, which has direct antimicrobial properties
• Compete with pathogenic organisms for space and nutrients, forming a protective barrier on the vaginal wall
• Support the immune system by modulating the local inflammatory response

When this community of lactobacilli is thriving, the vagina is remarkably self-regulating. Problems arise when the balance is disrupted and other organisms take over.

Bacterial vaginosis versus thrush: understanding the difference

Two of the most common conditions I see in clinic are bacterial vaginosis (BV) and vaginal thrush (candidiasis). Both involve a disruption of the vaginal microbiome, but they are fundamentally different conditions and require different treatments.

Bacterial vaginosis occurs when lactobacilli are displaced by an overgrowth of anaerobic bacteria, such as Gardnerella vaginalis and Atopobium vaginae. The hallmark symptoms are:

• A thin, greyish-white discharge
• A noticeable fishy odour, particularly after intercourse
• The vaginal pH rises above 4.5
• Interestingly, BV is often not associated with significant itching or soreness

Vaginal thrush is caused by an overgrowth of Candida species (most commonly Candida albicans), a yeast that is normally present in small amounts. Symptoms typically include:

• Thick, white, cottage cheese-like discharge
• Intense itching and irritation of the vulva and vagina
• Redness and swelling
• Stinging or burning during urination or intercourse

It is important to get the right diagnosis because the treatments are entirely different. BV is treated with antibiotics (metronidazole or clindamycin), while thrush is treated with antifungals (fluconazole or clotrimazole). Using the wrong treatment can make symptoms worse and further disrupt the microbiome.

What disrupts the vaginal microbiome?

The vaginal ecosystem is remarkably resilient, but a number of factors can tip the balance away from protective lactobacilli and towards problematic organisms:

• Antibiotics – while necessary for treating infections, antibiotics can deplete lactobacilli along with the harmful bacteria, leaving the vagina vulnerable to BV or thrush
• Douching and vaginal washing – the vagina is self-cleaning and does not need to be washed internally. Douching strips away beneficial bacteria and raises the pH
• Fragranced products – scented soaps, shower gels, bubble baths, intimate washes, and vaginal deodorants can all irritate the delicate vaginal tissue and disrupt the microbiome
• Spermicides and certain lubricants – some products contain ingredients that are harmful to lactobacilli
• Smoking – there is evidence that smoking is associated with lower levels of vaginal lactobacilli and an increased risk of BV
• Unprotected sexual intercourse – semen has an alkaline pH (around 7.2–8.0), which temporarily raises the vaginal pH and can shift the microbial balance
• Tight, non-breathable clothing – synthetic underwear and tight trousers can create a warm, moist environment that favours yeast overgrowth

Hormonal influences on vaginal health

Your hormones have a profound effect on your vaginal microbiome, and this is something many women are not aware of. Oestrogen is the key player: it stimulates the vaginal cells to produce glycogen, which lactobacilli ferment into lactic acid. When oestrogen levels are high, lactobacilli flourish; when oestrogen drops, the microbiome can become destabilised.

This hormonal relationship explains why the microbiome fluctuates at different stages of life:

• During the menstrual cycle – the microbiome is most stable in the oestrogen-dominant first half of the cycle and can shift around menstruation, when blood temporarily raises the vaginal pH
• During pregnancy – high oestrogen levels generally support a robust lactobacillus-dominated microbiome, which is thought to protect against ascending infections
• Postpartum – the sudden drop in hormones after delivery can disrupt the vaginal microbiome, contributing to the increased risk of infections in this period
• During perimenopause and menopause – declining oestrogen leads to reduced glycogen production, lower lactobacillus populations, rising vaginal pH, and increased susceptibility to BV, UTIs, and vaginal dryness (genitourinary syndrome of menopause)

For women experiencing vaginal symptoms related to menopause, local vaginal oestrogen (in the form of pessaries, cream, or a vaginal ring) can be remarkably effective at restoring the microbiome and relieving symptoms. It is one of the most under-prescribed treatments in gynaecology, and I encourage any woman experiencing these changes to discuss it with her doctor.

Probiotics: what does the evidence say?

There has been enormous interest in vaginal probiotics, and the market is flooded with products claiming to support vaginal health. As with many areas of wellness, the marketing has outpaced the science, but there are some promising findings.

The most studied probiotic strains for vaginal health are Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14, which have been shown in some clinical trials to reduce the recurrence of BV when taken orally or used vaginally alongside standard antibiotic treatment. However, the evidence is not yet strong enough to make probiotics a routine recommendation.

What I tell my patients is this:

• Probiotics are not a substitute for treating an active infection – if you have symptoms, you need a proper diagnosis and appropriate treatment first
• If you experience recurrent BV, there is reasonable evidence to support trying a lactobacillus-based probiotic alongside antibiotic treatment, either orally or vaginally
• Not all probiotic products are equal – look for products that specify the strain (not just the species) and that have some clinical evidence behind them
• A diet rich in fibre and fermented foods (yoghurt, kefir, sauerkraut) supports your overall gut microbiome, which in turn influences vaginal health

The field of vaginal microbiome research is evolving rapidly, and I expect we will have much more refined recommendations in the coming years.

Practical tips for maintaining vaginal health

Based on the current evidence, here is what I recommend to my patients for supporting a healthy vaginal microbiome:

• Wash the vulva with water only, or at most a gentle, unfragranced wash. Never wash inside the vagina
• Wear cotton underwear and avoid tight-fitting synthetic clothing where possible
• Change out of damp clothing (swimwear, gym clothes) promptly
• Use condoms to reduce the impact of semen on vaginal pH and to protect against sexually transmitted infections
• Choose pH-balanced, glycerin-free lubricants if you use them
• Wipe from front to back after using the toilet to prevent bowel bacteria from entering the vagina
• Avoid unnecessary antibiotics – only take them when genuinely needed and prescribed
• Do not smoke – this is yet another reason to consider quitting
• Discuss vaginal oestrogen with your doctor if you are perimenopausal or postmenopausal and experiencing vaginal dryness or recurrent infections

If you are experiencing recurrent symptoms – whether that is recurrent thrush, persistent discharge, ongoing irritation, or a pattern of BV that keeps returning – it is worth seeking a thorough assessment. Sometimes what appears to be a straightforward infection has an underlying cause that needs to be addressed, and a detailed history and appropriate testing can make all the difference.