Think of it as a tiny, protective shield for your lady parts.

Most women have never heard of their “vaginal biofilm,” but it’s an important part of their health, influencing symptoms like vaginal odor, discharge or recurring infections.

“[It’s] a thin, sticky layer of bacteria that can attach to the vaginal lining and protect itself by producing a kind of shield,” OB-GYN Dr. Kate McLean told The Post.

“Think of it like a microscopic community of bacteria living under a protective coating,” she added, noting that you can’t see or feel it yourself, but you definitely feel its impact.

When bad bacteria form microfilms, it can cause difficult-to-treat bacterial vaginosis (BV) and yeast infections. When beneficial bacteria like lactobacilli make them, it blocks bad bacteria from taking hold.

“Not all biofilms are harmful, but some can become problematic,” said McLean, a board-certified obstetrician-gynecologist and Chief Medical Officer at Evvy.

“The biofilm can make it harder for the body, or even medications, to fully clear that negative bacteria in your body. This is one reason some people experience recurring vaginal symptoms even after treatment.”

Here’s what to know about maintaining the delicate balance and protecting your vagina.

Don’t worry, bacteria are supposed to be there

Biofilms are “a normal part of life,” McLean says. They’re everywhere, from dental plaque on your teeth to deep in the gut to on top of the skin.

Society is cleaner than it’s ever been, which can make it tempting to see bacteria as an enemy.

But there is such a thing as being too clean. Many doctors urge women not to douche for this reason: While trying to be clean or eliminate odor, douching actually kills good bacteria in the vagina.

“One of the biggest misconceptions is that vaginas should be completely odorless or that any discharge is a sign that something is wrong,” McLean said. “In reality, healthy vaginas have a natural scent, and discharge is often a normal and important part of vaginal function.”

Another thing thing to note: Recurring vaginal symptoms actually have little to do with poor hygiene, McLean said.

“They’re usually driven by complex biological factors, including the vaginal microbiome, and often have very little to do with cleanliness,” she said.

Battle of the bacteria

How do you keep a healthy vaginal microbiome? With lots of lactobacilli.

This “good” bacteria produces lactic acid, bringing down the pH of the vagina, plus hydrogen peroxide and bacteriocins, all making the environment inhospitable to undesirable bacteria.

Perhaps most importantly, it makes a biofilm of its own, blocking the real estate from getting taken up by bad bacteria.

But the tides can turn quickly. Disruptions to the microbiome like antibiotic use, douching, even unprotected sex, can harm the lactobacilli populations, allowing others to flourish.

Anaerobic bacteria like Gardnerella vaginalis, Atopobium vaginae, and Prevotella spp. can team up to make biofilms and cause infections, particularly BV. This might appear as grey or white discharge, a fishy odor, and itching or burning while urinating.

Without lactobacilli, yeast can grow too, causing similar symptoms. And bad bacteria growing out of control can easily migrate to the urinary tract, causing a UTI, as well.

How can biofilms create repeat infections?

Biofilms can make bad bacteria 1,000 times more tolerant to antibiotics or antifungals. This happens because treatment might successfully eliminate the surface of the biofilm, but doesn’t fully eliminate the problem.

“Bacteria form biofilms as a survival strategy … This shield can make it easier for them to resist changes in their environment and protect themselves from being washed away,” said McLean.

Biofilms can also avoid detection by weakening immune responses and tricking the immune system into thinking the biofilm is not a threat while it’s actually laying dormant.

Once the threat is gone, the bad bacteria flourishes once again. As much as 60% of women with BV experience a repeat infection within a year of treatment.

Go to the doctor if you’re dealing with persistent symptoms, McLean says. They’ll need to investigate to understand the source of the problem. If it’s BV, they’ll likely prescribe an antibiotic that can be taken orally or inserted into the vagina.

Long term, protect your vagina by “supporting a healthy vaginal microbiome—by avoiding unnecessary disruption, getting appropriate care when symptoms arise, and understanding your unique microbiome,” she said.