We know that common vaginal infections such as yeast infections (also known as thrush/ candidiasis) and bacterial vaginosis occur when the healthy bacteria in your vagina are disrupted, allowing the bad bacteria to dominate which causes an infection.

Unfortunately, everyday life including use of antibiotics, hormonal imbalance1, lifestyle and even sex can lead to an overgrowth of bad bacteria which can put your vaginal microbiome in danger.

While antibiotics and antifungal treatments eliminate bad bacteria, they also wipe out the good bacteria in order to do so. Probiotics help to repopulate the vagina with healthy bacteria. Vaginas with healthy bacteria have a reduced chance of getting an infection and can recover better from an infection.

Sadly, vaginal infections do have a tendency to reoccur, and this is where vaginal probiotics are particularly useful to boost the vaginal microbiome with healthy bacteria. They are also helpful to boost the microbiome after a course of antibiotics.

In this article we cover:

  1. Choosing the right strains of bacteria for a vaginal probiotic (including a breakdown of what each strain does) and why yogurt is a bad idea
  2. Why more bacteria in your vagina is not necessarily better
  3. What actually happens in the vagina?
  4. Oral capsules vs vaginal pessaries – how to establish what’s right for you?
  5. What’s the difference between tablets, capsules and gels – and why does this matter?

Choose the right strains, and why is yogurt not a smart idea

The vaginal microbiome has a low biodiversity (a few prominent species and a low number of other species) with most of the bugs in a vagina belonging to Lactobacillus (L.) genus.

But not all Lactobacillus species can colonise in the vagina. It’s important that the “good” bugs stick around, populate and live happily in the vaginal microbiome.

The species that colonise almost every single healthy vagina across the globe2 are Lactobacillus crispatus and Lactobacillus gasseri. L. crispatus and L. gasseri have excellent adhesive abilities to the vaginal wall cells and create the most dominant healthy bacterial colonies. In fact, L. crispatus is known by some scientists affectionately as the ‘superhero’ of the vagina and the most beneficial healthy bacteria in vaginal microbiome. L. crispatus is present in healthy vaginal microbiome of 65% of women while L. gasseri is present in more than 40% of women2.

In addition to L. crispatus and L. gasseri, there are ‘fighter’ bugs producing substances that can disrupt biofilms created by bad bacteria. Biofilms are a protective layer that bacteria can generate to help protect themselves, which is one of the reasons why sometimes prescription therapy may not eliminate all bad bacteria.  L. rhamnosus, GR-1® and L. reuteri, RC-14® are two of these good ‘fighter’ vaginal bacterial strains whose beneficial effect on vaginal health has been well documented through numerous clinical trials and are beneficial in fighting pathogens.

Should you use yogurt to treat a yeast or bacterial infection?

So, is the use of yogurt on a tampon really an old wives' tale? We investigate:

As far as yogurt is concerned, two studies of yogurt douching, and one study of orally ingested yogurt suggest clinical benefit for bacterial vaginosis3. The probiotic strain examined was L. acidophilus.

Another study evaluated the use of yogurt which contained L. casei and found that it reduced vaginal fungal colonisation4.

So why aren’t we all using yogurt to treat bacterial vaginosis? Well there are a few problems with the use of yogurt in promoting vaginal health.

  1. Yogurt is a food product, and food products are much less regulated than therapeutic goods, which are registered with TGA. L. acidophilus may not be in the product at all as advertised and it will be difficult to establish if the right L. acidophilus strain is present.
  2. An in-vitro study demonstrated poor adherence to human vaginal wall cells of L. acidophilus from a yogurt compared with L. acidophilus from a therapeutic tablet5.
  3. Applied orally, yogurt presents an issue for lactose intolerant women.
  4. Not all strains of L. acidophilus will have the same beneficial effect on vaginal health6.
  5. Simply, yogurt is just not good enough.

Key take out: Look for a pessary probiotic with healthy bugs: L. crispatus & L. gasseri plus fighter bugs, L. rhamnosus, GR-1® and L. reuteri, RC-14®

How many bugs do I need? Why ‘more’ is not necessarily better

It would be natural to think that applying all beneficial vaginal strains all at once and in large concentrations would make for a more effective vaginal probiotic product.

But “more” is not necessarily always better.

Why is that, you ask?  

Applying a mixture of many different vaginal probiotic strains will result in greater competition between bugs for food and territory in the vaginal tract. This can prevent successful colonisation or function of probiotics as many may die without food.

Good quality probiotics will take guidance of quantities of bugs in a healthy vaginal microbiome as researched in clinical trials and provide a food source, also known as prebiotics, in their formulation.  

A good vaginal probiotic will contain the right strains, a balanced combination of strains, and the necessary quantities of bug food.

What actually happens in the vagina to trigger a vaginal infection (and how a probiotic works to reverse it)?

In a nutshell, here’s is what is happening in a vagina at any given moment:

  1. Microbiome disturbance. When the vaginal microbiome is disturbed, good bugs (lactobacillus species) will start decreasing. The lactobacillus genus is known for secreting lactic acid, which is responsible for keeping the vaginal pH in a nice and low acidic range.
  2. With an increasing pH over 4.5, those bad bugs have more chance of survival. An increase in pathogen bacteria can lead to bacterial vaginosis and other vaginal infections.
  3. The diminishing of good colonies gives pathogenic yeast a chance to boost its growth causing thrush or yeast infections.
  4. The application of a vaginal probiotic is reversing this process. The battle for restoring balance and health in a vagina is happening on several fronts. Not just that good bacteria take over the territory and establish dominant colonies, they will also secrete antibiotic-like compounds that can attack pathogens directly, boost local immune system and disrupt pathogenic strongholds – biofilms. With secretion of lactic acid, vaginal pH will decrease and create an environment that is antagonistic to pathogens. Essentially the good bugs win.

Vaginal Pessaries vs Oral Probiotics – what’s the difference in effectiveness?

Vaginal route of administration, either through a pessary, gel or tablet, allows for targeted and direct delivery of probiotic strains into the vagina. Clinical data supports the benefit of vaginal administration of probiotics.

Being at the site of action, good bugs can directly replenish the vagina’s environment by colonising it and producing beneficial substances, like lactic acid, that would further protect and support healthy vaginal microbiome.

Oral probiotics often have similar strains to vaginal pessary probiotics, but they need to go through the gastric system to get to the vagina. As the gastric system is quite a harsh, acidic environment, many of the good bugs from the probiotic may die before they reach the site of action in the vagina.      

And while studies have shown oral probiotics do colonise in the vagina eventually, it can take longer than vaginal pessaries7.  Vaginal administered probiotics are usually administered less frequently and for shorter periods of time (5-10 days). Orally administered probiotics are usually applied over course of 30 to 60 days.

The results from two clinical trials done on women with bacterial vaginosis showed that direct vaginal application of L. rhamnosus, GR-1® and L. reuteri, RC-14® strains was much more efficient in restoring healthy vaginal microbiome compared with oral administration (88% vs. 51%)8.

Vaginal Pessary Probiotics vs Oral Probiotics - What's the difference in effectiveness?

Vaginal probiotics taken orally follow a different pathway on their way to the vagina. Bacteria needs to go through the whole gastrointestinal tract, come out through anus and be smeared forward into vagina9.

Understanding the pathway that vaginal probiotics taken orally have to travel in order to get to the vagina

There are a few downsides with oral route of administration:

  1. The ability of probiotic strains to survive passage through the gastrointestinal tract becomes an important selection factor, and it’s difficult to ascertain what percentage of applied dose eventually reaches vagina. 
  2. The beneficial effect of oral probiotics is more likely achieved through the support of the immune system and is lacking direct good bacteria-bad bacteria interaction10.
  3. Pathogenic bacteria are following the same route as the healthy bacteria.

What’s the difference between tablets, capsules and gels – and why does this matter?

There are many probiotic products on the market claiming beneficial effect for vaginal health. The reality is that quality, viability, strain selection and colonisation capabilities of many of those products are not reliable11.

When it comes to vaginal application of probiotics, the choice of dosage form is critically important to ensure a positive health outcome, survival of the healthy bacterial strains, shelf-life stability and safety for a patient.

Probiotics are incredibly sensitive organisms, needing the right environment both during the manufacturing process and during shelf-life, in the primary packaging to give them the best chance of survival over the lifetime of the product.

The following are risk factors that may limit the survival of good bacteria:

  • Moisture. Water is the number one enemy of probiotics which can mean that gels and creams claiming probiotic benefits deliver a diminished dose to the patient. 
  • Heat. Heat can be generated during the manufacturing process when a tablet is compressed together, and this can cause the bugs to die.
  • In some homeopathic tablets the probiotic is described as a ‘non-active’ ingredient so it’s good to be aware of this and aim to purchase a probiotic with active strains.
  • Packaging is also important. A blister pack with aluminium foil on both sides is the superior protection for probiotics. Shelf-stable probiotics also do not require refrigeration which can lower the risk of destabilising the product with temperature variants caused by transportation and taking it in and out of the fridge.

In this table we compare tablets, capsules and gels as dosage forms for probiotics. 

Comparison of vaginally applied probiotics in tablet, capsule and gel form

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See list of references used on this page

1  Farage, M. A., Miller, K. W. & Sobel, J. D. Dynamics of the vaginal ecosystem—hormonal influences. Infect. Dis. (Auckl.)3, IDRT.S3903 (2010).

2 Ravel J, Gajer P, Abdo Z, Schneider GM, Koenig SS, McCulle SL, Karlebach S, Gorle R, Russell J, Tacket CO, Brotman RM, Davis CC, Ault K, Peralta L, Forney LJ. Vaginal microbiome of reproductive-age women. Proc NatlAcadSci U S A. 2011 Mar 15;108 Suppl 1(Suppl 1):4680-7.

3 Nassim Assefi, MD.Yogurt for Vaginitis. ReliasMedia, October 2001; Volume 4; 109-112

4 Hu H, Merenstein DJ, Wang C, Hamilton PR, Blackmon ML, Chen H, Calderone RA, Li D. Impact of eating probiotic yogurt on colonization by Candida species of the oral and vaginal mucosa in HIV-infected and HIV-uninfected women. Mycopathologia. 2013 Oct;176(3-4):175-81. 

5 Wood JR, Sweet RL, Catena A, Hadley WK, Robbie M. In vitro adherence of Lactobacillus species to vaginal epithelial cells. Am J Obstet Gynecol. 1985 Dec 1;153(7):740-3. 

6 McLean NW, Rosenstein IJ. Characterisation and selection of a Lactobacillus species to re-colonise the vagina of women with recurrent bacterial vaginosis. J Med Microbiol. 2000 Jun;49(6):543-552. 

7 Borges S, Silva J, Teixeira P.The role of lactobacilli and probiotics in maintaining vaginal health. Arch Gynecol Obstet 2014;289(3):479-489.

8 Wu, S, Hugerth, L.W., Schuppe-Koistinen, I.et al. The right bug in the right place: opportunities for bacterial vaginosis treatment. NPJ Biofilms Microbiomes 8, 34 (2022).

9 Bastani, P. et al. Dairy Probiotic Foods and Bacterial Vaginosis: A Review on Mechanism of Action, in E. C.  Rigobelo (ed.), Probiotics, IntechOpen, London. 2012. doi: 10.5772/50083.

10 Reid, G. et al. Oral use of Lactobacillus rhamnosus GR-1 and L. fermentum RC-14 significantly alters vaginal flora: randomized, placebo-controlled trial in 64 healthy women. FEMS Immunol. Med. Microbiol.35, 131–134 (2003).

11 Reid G, Bruce AW. Selection of Lactobacillus Strains for Urogenital Probiotic Applications. TheJournal of Infectious Diseases, Volume 183, Issue Supplement_1, March 2001, Pages S77–S80.