Why BV Keeps Coming Back: Expert Insights from Dr Phillip Hay

You've taken the antibiotics. You've worn organic cotton underwear. Tried all the remedies. Perhaps felt some relief. And then - sometimes within weeks - the whole frustrating cycle starts again.

If this sounds familiar, you're not alone. Bacterial vaginosis (BV) affects 1 in 3 women of reproductive age¹ and, for many of us, it's not a one-off experience.

So why does BV keep coming back? To get real answers, our founder Lucy Hope sat down with Dr Phillip Hay, one of the world’s leading experts in bacterial vaginosis, recurrent thrush and sexually transmitted infections. He’s a consultant at Guy’s and St. Thomas’ with decades of clinical and academic experience. His work has shaped international guidelines on diagnosing and treating vaginal infections. Like us at The Daughters of Mars, his research includes how we might use new non-antibiotic approaches, like lactoferrin, to treat and prevent BV and thrush.

What follows is a clear, science-backed, shame-free guide to what BV actually is, why it persists, and where research is directing potential treatment options.

(You can watch the full interview below.)

Read the full transcript here.

What Exactly Is BV?

Let's start with the basics. BV is an imbalance in your vaginal microbiome - that's the community of bacteria naturally living in your vagina (and yes, they're supposed to be there).

When things are balanced, protective Lactobacillus bacteria dominate, producing lactic acid that keeps vaginal pH low and harmful microbes in check. It's a beautiful system when it works.

But when that balance is disrupted, other bacteria (such as Gardnerella vaginalis, Prevotella, or Fannyhessea vaginae) grow unchecked. The result is BV.

Some women experience no symptoms at all. For others, BV presents with:

Abnormal discharge (often thin, white or grey)
A distinct "fishy" odour, especially after sex
Itching or irritation (though this is less common)

Diagnosis is made by a clinician, often by checking pH (BV usually raises it above 4.5) or examining vaginal samples under a microscope.

And here's the bit that really matters: BV isn't just uncomfortable. It's been linked to increased risk of HIV, PCOS, endometriosis, gynaecological cancers, pelvic inflammatory disease, infertility and adverse pregnancy outcomes including preterm birth².

Why Does BV Keep Coming Back?

Recurrence is frustratingly common - 50% of women relapse within 3-6 months³ and up to 70% within a year². Dr Hay explains why:

1. Menstruation (Bacterial Vaginosis loves blood)

"BV loves blood" - Dr Hay uses this memorable phrase to describe what many women with recurrent BV already know: their symptoms consistently return with their period, and there's solid science explaining why.

Menstrual blood is alkaline and rich in iron - both of which create ideal conditions for BV-associated bacteria to thrive. But it's not just the blood itself: hormonal shifts during your period also weaken your vaginal microbiome's natural defences. Oestrogen supports those protective lactobacilli by feeding them glycogen (a form of sugar stored in vaginal cells). When oestrogen dips during your period (or later in menopause), that protection diminishes, leaving your microbiome vulnerable.

If you've noticed BV flaring up around your period, now you know why.

2. Biofilms

BV bacteria form sticky biofilms that shield them from antibiotics. Even after a course of treatment, these bacteria can persist and re-establish once conditions are favourable again⁴. Antibiotics can clear the surface bacteria, but the underlying biofilm structure remains intact, ready to repopulate. It's like trying to clean mould with a surface spray when the spores are embedded in the wall. This resilience is one of the reasons recurrence is so high.

3. Sex and Partners

(Why treating your BV might mean treating their foreskin)

You may have heard that BV isn't an STI and while that's technically true, the science is more nuanced. When asked whether BV is an STI, Dr Hay says: "I tend to sit on the fence and say: sometimes it is and sometimes it isn't."

BV is at least sexually associated and is more common in sexually active women. Epidemiological data strongly suggest that BV behaves like a sexually transmitted infection², with transmission likely between partners.

What we know: alkaline semen alters vaginal pH. Partners, particularly uncircumcised men, can harbour BV-associated bacteria under the foreskin, potentially reintroducing them during intercourse¹. "I’ve been saying for years that the only intervention reducing the prevalence of BV in women is male circumcision, though there’s unlikely to be wide uptake! A secondary analysis of a study looking at male circumcision to reduce HIV infections in sub Saharan Africa showed a 40% reduction in BV rates in female partners following circumcision.

But here's the good news: you don't need drastic measures. Recent research from Australia's StepUp trial shows real promise. When male partners received combination treatment (oral metronidazole plus topical clindamycin), there was a 50% reduction in BV recurrence in female partners⁶. It's not a complete cure - there was still 50% relapse at four months - but it represents significant progress in breaking the reinfection cycle.

4. The Womb and Gut Connection

Some of the bacteria linked to BV can also live in the uterus and gut. This may make BV harder to fully clear, because the bacteria could return to the vagina after treatment. Scientists are still studying how significant these hidden reservoirs really are.

Why Common "Cures" Don't Work

Walk into a pharmacy or fall down a wellness rabbit hole online and you'll find plenty of DIY "cures" for BV: yoghurt, garlic, cranberry juice, perfumed washes (yikes). According to Dr Hay, none of them work.

In his "rating game" during the interview, Dr Hay gives douching and scented vaginal washes a firm 0/10, along with low scores for several folk remedies.

The vagina is self-cleaning (yes, truly - our vaginas are remarkable). Interventions that flush or mask odour often strip away protective lactobacilli, making recurrence more likely. These "remedies" don't restore balance. In many cases, they actively sabotage it.

Treatment Today

Standard treatment for BV remains antibiotics (metronidazole or clindamycin, taken orally or vaginally). They're effective in the short term, but the high recurrence rate shows their limitation: they clear bacteria, but they don't restore balance to the microbiome.

Dr Hay is particularly cautious about current guidelines: "Current guidelines still recommend oral metronidazole as first-line treatment. I think future generations will say we were mad to use metronidazole for BV." He expresses concern about broad-spectrum antibiotics disturbing gut microflora and breeding resistance.

His preference? "I'm much more a fan of dequalinium chloride - more an antiseptic than an antibiotic. It's a licensed treatment for BV, isn't absorbed into the bloodstream, acts locally in the vagina, and doesn't upset the rest of the body's microbiome."

Antibiotics also don't distinguish between good and bad bacteria. They wipe out both, leaving the vaginal microbiome depleted - which is why they're often only a short-term fix³.

Ironically, this can create a loop: every course of antibiotics knocks out the protective species along with the harmful ones, making it easier for BV-linked bacteria to move back in and trigger yet another episode.

The Future of BV Care

The good news? Research is finally moving towards treatments that actually work with your vaginal microbiome, not against it:

Lactoferrin: a natural protein nicknamed "pink gold" that binds iron, essentially starving BV bacteria of the nutrient they thrive on. Unlike antibiotics, lactoferrin doesn't harm protective lactobacilli - making it a promising microbiome-friendly approach, particularly for supportive or preventive care rather than rapid acute treatment.
Probiotics: particularly vaginal delivery of Lactobacillus crispatus, shown to recolonise the vagina and stabilise the microbiome.
Partner treatment: the Australian StepUp trial found that treating male partners with combination therapy reduced female BV recurrence by 50%⁶. While not a complete cure, this represents the first successful evidence that partner treatment can reduce rapid relapse.
Better diagnostics: as Dr Hay emphasises, "cheap home test kits would be wonderful" - rapid tests that detect imbalance early, before symptoms spiral.

Dr Hay sums up his vision for the future: "Good diagnostics. Better treatments - more supportive and physiological rather than blunderbuss antibiotics. Learn to love and support [the vaginal microbiome]. Don't go for drastic measures - you need gentle support."

Breaking the Silence

BV isn't rare. Yet shame and silence keep too many women confused, embarrassed and stuck with misinformation.

Dr Hay's work - and the growing field of vaginal microbiome science - shows us that recurrence isn't inevitable. It's a solvable problem. We just need better solutions.

At The Daughters of Mars, we believe in a future where women's health products are designed to proactively support the vaginal microbiome.

References

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