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Vaginal pH Redux: Acidic Tampons, Coming to a Store Near You

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A woman's purse contents, including the ubiquitous emergency tampon.

A woman's purse contents, including the ubiquitous emergency tampon. Image by Helga Weber, protected by a Creative Commons license.

Readers of this blog are already aware that their vaginas are at their best when they are on the acidic side. Vaginal flora is healthy, bacterial overgrowth is at a minimum, and any foreign bodies that want to pass through are firmly discouraged. Semen and douching can increase pH, douching especially so since the liquid used to douche not only has a relatively high pH but flushes out normal, good bacteria.

If there are substances that increase vaginal pH, might other substances decrease vaginal pH and thus encourage the growth of normal flora?

RepHresh thinks so. RepHresh is a company that makes pH-balancing gels and cleansers for your ladyparts. Recently, they started carrying a new product, RepHresh Brilliant, which is a pH-balancing tampon (hat tip to my undergraduate Sophia Bodnar for being the first to tell me about it). They claim that menses increases pH, and thus a tampon that decreases pH will keep bacterial overgrowth in check. The RepHresh Brilliant tampon contains strips of material that slowly release lactic acid and citric acid as they are saturated with menstrual fluid.

It certainly sounds like a good idea. Women in industrial and post-industrial environments menstruate far more often than we probably did under ancestral conditions, due in part to an energy surfeit (you know, eating too much chocolate while sitting at a desk, which is exactly what I was doing while drafting this post) and in part due to modern reproductive decisions (you don’t menstruate so much if you’re pregnant or breastfeeding all the time) (Strassmann 1997). So about 400 times in our lives, for several days at a time, we have a higher pH (somewhere between a 5.3-6.6 depending on the day according to Wagner and Ottesen 1982) than is ideal for housing beneficial vaginal flora.

But I want to know if this fancy tampon works. 1) Does it reduce pH, 2) does it do so without side effects, and 3) does it have an effect on vaginal flora?

Tl;dr version:1)  yes, 2) probably, and 3) not sure.

RepHresh’s own research on the topic

A single paper tests the efficacy and safety of the RepHresh Brilliant tampon, and you can find a copy on the RepHresh site (Brzezinski et al. 2004). The authors found that participants who used the test-tampon (the one with strips that release lactic and citric acid) did not have significantly higher vaginal pH during menses (p = 0.0518), while participants who used a regular tampon did (p = 0.0011). Saying that first result isn’t statistically significant is adhering to the 0.05 alpha without honoring the spirit of the 0.05 alpha – it is not statistically significant but in a way that makes one question the meaning of statistical significance. (If you are new to statistics, usually a p-value that falls below 0.05 is considered significant, so a p-value of 0.0518 is pretty darn close, and in fact most people would drop those last two places and round to the hundredth, rendering that analysis p = 0.05, or statistically significant.) All that said, the difference between groups in intra-menstrual pH is statistically significant (p = 0.0025). And lowering menstrual pH by 0.5 isn’t bad.

Brzezinski et al 2004 Table 1, which shows the average vaginal and tampon pH in women using regular tampons and the test tampons.

Brzezinski et al 2004 Table 1

Further, according to Brzezinski et al (2004), no participants complained of vaginal irritation, which would be my big worry about an acid-producing tampon. And no participants in either group had abnormal vaginal flora during the study.

So, yay! Acid-increasing tampons for everyone! Kinda.

Nits to pick

First, the authors of this study did not use the gold standard method for assessing vaginal irritation or endothelial disruption, which is a colposcopy, or visual assessment of the vaginal tissue. Instead, the authors relied on self-report. Minor issues, or ones that could develop with repeated use over many cycles, would be caught in a longitudinal study that used this method. But this study only assessed side effects and pH reduction in a single cycle. And as far as I can tell, it is the only published study on the topic.

The second issue to consider is that all twenty eight participants had normal vaginal flora. The coincidence of all participants being perfectly healthy makes me wonder if a small sample size caught an abnormal number of normal women, or if they needed more rigorous testing of the bacterial swabs. But the study authors provide no detail about how they determined this or whether they assessed absolute and relative quantities of different bacteria that comprise normal flora. So, the normal flora in every single subject could just be that all twenty eight women were very healthy, but in every other study I read in preparing for this post, there were always a significant minority of participants who had or developed abnormal flora. I just wish the authors had provided more detail here.

Finally, this research was funded by Rostam Ltd Israel, a corporation that makes tampons. I did a little digging to try and figure out the relationship between Rostam and RepHresh. Rostam was bought by Albaad Massuot Yitzhak Ltd in 2010. Yet RepHresh has an article about the Rostam Ela tampon in the Wall Street Journal on the website from 2004. So my best guess (and someone with more business savvy than me could probably figure this out) is that RepHresh bought the Ela tampon from Rostam some time between 2004 and 2010, and is now marketing it as RepHresh Brilliant. Either way, part of the funding for the research was from a corporation invested in seeing the tampon gain FDA approval in the US. The 2004 article that RepHresh has on its site (scroll to the “Articles” and click the link for the pdf) explains that the testing for this tampon was simply to demonstrate it is as safe as effective as any regular tampon, since it is being categorized as a medical device.

I’m not worried about the lactic acid, since that is a product of Lactobacilli, which is not only present in normal vaginal flora but particularly good for the ladyparts (McLean and Rosenstein 2000; Onderdonk et al. 1986; Valore et al. 2002). But I am worried about the citric acid, since it produces moderate irritation and damage to the epithelium, and increases permeability and absorption rates when used to enhance drug delivery (Richardson et al. 1989). Maybe it’s shouldn’t be concerning in the particular way it is released in the RepHresh Brilliant tampon. I honestly don’t know.

I certainly am happy to see a company taking a woman’s actual vaginal pH into account in the making of their products. Give the tampon a try if you are so inclined, and let me know how it goes. I think I’m going to just let my vagina regulate itself, since vaginal flora repopulates naturally and quickly after menses on its own (Keane et al. 1997; Onderdonk et al. 1986; Wagner and Ottesen 1982).


Brzezinski A, Stern T, Arbel R, Rahav G, and Benita S. 2004. Efficacy of a novel pH-buffering tampon in preserving the acidic vaginal pH during menstruation. International Journal of Gynecology and Obstetrics 85(3):298-300.

Keane F, Ison C, and Taylor-Robinson D. 1997. A longitudinal study of the vaginal flora over a menstrual cycle. International Journal of STD and AIDS 8(8):489-494.

McLean N, and Rosenstein I. 2000. Characterisation and selection of a Lactobacillus species to re-colonise the vagina of women with recurrent bacterial vaginosis. J Med Microbiol 49:543-552.

Onderdonk A, Zamarchi G, Walsh J, Mellor R, Munoz A, and Kass E. 1986. Methods for quantitative and qualitative evaluation of vaginal microflora during menstruation. Applied and Environmental Microbiology 51(2):333-339.

Richardson JL, Minhas PS, Thomas NW, and Illum L. 1989. Vaginal administration of gentamicin to rats. Pharmaceutical and morphological studies using absorption enhancers. International Journal of Pharmaceutics 56(1):29-35.

Strassmann BI. 1997. The biology of menstruation in Homo sapiens: Total lifetime menses, fecundity, and nonsynchrony in a natural-fertility population. Current Anthropology 38(1):123-129.

Valore E, Park C, Igreti S, and Ganz T. 2002. Antimicrobial components of vaginal fluid. Am J Obstet Gynecol 187:561-568.

Wagner G, and Ottesen B. 1982. Vaginal physiology during menstruation. Annals of Internal Medicine 96(Part 2):921-923.

Kate Clancy About the Author: Dr. Kate Clancy is an Assistant Professor of Anthropology at the University of Illinois. She studies the evolutionary medicine of women’s reproductive physiology, and blogs about her field, the evolution of human behavior and issues for women in science. Find her comment policy here. Follow on Twitter @KateClancy.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. notanester 5:51 pm 02/24/2012

    So… if it is the uterine tissue and blood that increases pH (and not the tampon, which is what I thought would be the culprit), is it a good idea to put some lactic acid in a menstrual cup and lower your vaginal pH? (I’m just throwing a thought out). Since the menstrual cup also holds fluid for some time, would it be just as prone to causing infections as tampons?

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  2. 2. kclancy 10:22 pm 02/24/2012

    notanester, that’s an excellent question. There are studies that look at the precursor to lactic acid — Lactobacilli — and develop strains that are maximally effective in regulating vaginal flora. So probiotics have been shown to work (I’ve even heard of women making a plain yogurt “popsicle” and using it as a suppository). It makes sense that swishing around a little lactic acid should have a similar effect. I just wonder what else Lactobacilli does besides regulate acidity of the environment. So that makes me think it’s better to put the good bacteria in there than just the acid. But I really don’t know!

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  3. 3. kclancy 10:23 pm 02/24/2012

    Oh, oh I did just remember one thing. I read a study while researching this post that showed that just using a little acid only temporarily reduces pH, which the study authors then suspected wouldn’t be that helpful. I think that’s part of the reason this tampon uses a time-release mechanism. So the menstrual cup idea may only have a temporary effect, though I guess if it’s sloshing around in there it’s hitting the vaginal wall over an extended period of time :) .

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  4. 4. ThomasH 3:44 am 02/25/2012

    It appears to me that there is are bigger problems with the author’s data analysis than the p-value issue that you raise. The question the research attempts to address is whether or not use of the tampon reduces the change in intra-menstrual pH by a significant amount. Of all the p-values tossed around in the paper, only one addresses this: the comparison of differences, which is addressed by the statement “The difference in the changes of vaginal pH in the regular vs. test tampon group (0.98 vs. 0.32) was highly statistically significant (P=0.0011).”

    Since the authors leave off how they calculated the difference (is this the difference of the means, or the mean of individual differences?), any estimate of the standard deviation of the differences, and even what test they used to arrive at this p-value, we are unable to evaluate whether or not the RepHresh tampon is really effective at limiting the increase in vaginal pH. The correct analysis (or, at least, the best one that I can think of) would have taken the difference between intra-menstrual and baseline values for each subject and performed a t-test across the treatments. It appears that this was not done.

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  5. 5. CrystalVoodoo 1:03 pm 02/25/2012

    I purchased a box awhile back thinking that it was at least scientifically sound. There was a minor reduction of irritation on lower flow days but nothing that would make me tout its effectiveness to the general public. In my opinion if there isn’t a specific reason for needing it then there isn’t much benefit over other products.

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  6. 6. Mike Barry 7:52 pm 02/25/2012

    I have never heard the term before, but can’t help finding it rather poetic – vaginal flora.

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  7. 7. Dr. Cosmic 10:03 pm 02/25/2012

    Another thing with citric acid in it! :0 It’s corrosive and a chelating agent. Is that what your vagina really needs?

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  8. 8. GG 12:52 am 02/26/2012

    Yeah, stick your tampons into yogurt to make them “pro-biotic” lol…

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  9. 9. Kate Clancy in reply to Kate Clancy 12:11 pm 02/27/2012

    ThomasH, what a great point, I totally missed it when analyzing the paper myself. Thanks for pointing that out!

    Crystal, glad to hear you had no major problems with the tampons.

    dhbone, good point about what “pH-balanced” means — I do think it’s a misleading term. And thanks for the kind words about the post — I do occasionally use words like “ladybusiness” and even sometimes “lady parts,” but in a way I hope is sarcastic rather than fully embracing the term. (Edited to add: Oops — from my dashboard I thought dhbone was commenting on this recent post — this comment was on the previous post on vaginal flora – have reposted this comment there.)

    Mike — I know! And preferable, I think, to vaginal fauna :) .

    Dr. Cosmic, I agree. I’ve started paying attention to whether it’s in any of the products I buy since writing this post (happened to have the chance to choose between two eye creams over the weekend, and chose the one with fewer known irritants, including citric acid).

    And GG — strangely enough, there are women who do stick their tampons in yogurt, or make yogurt “popsicles” and put them into their vaginas to help them restore vaginal flora. Or I shouldn’t say “strange” because it does make sense, since Lactobacilli are in yogurt and are a major percentage of the bacteria in a healthy vagina. :)

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  10. 10. Kvnptrck 12:59 pm 02/27/2012

    A test and a control with a sample size of 14? I could calculate a p-value on a study with 5 people if I wanted, it doesn’t mean that my findings a relevant. It would be one thing if there was a shortage of females, but if you’re doing a study on a population that is so large then you really need to do a little better than comparing 14 as a control vs 14 as a test. It would be one thing if we were talking about some group of people with a super rare genetic mutation or SNP or something like that but 14 is not even close to properly representing the population. Think of it this way: if there’s a side effect that occurs in 30% of girls in menses, it would be pretty easy to not see as much as one person of those 14 exhibit such a side effect. 7 out of 10 is 70%. 14 out of 20 is 70%. If I flip a coin 20 times and get 14 heads, is my coin weighted? Did somebody devise this coin specifically for the purpose of getting heads more often? They very well could have, but I would not be confident to the point where I’d put my life on the line or call anyone a cheater until a higher sample size (i.e., 140 flips, 1400 flips, 14,000 flips) was taken. It’s not all about p-value and I’m sure they know that (or need to fire some people). If these 14 people magically gave a p-value that was true of the population, then they have no reason NOT to use a bigger sample size. Increasing n (n = sample size btw) will decrease p value. If a study’s findings are consistent, then the p-value at n=14, will be higher than if n=1400. Higher p-value is bad for selling your product. They want to sell ther product, therefore they should want to increase their p-value. So either 1) they don’t care, 2) they found something that they didn’t want to find, or 3) whoever analyzed the data/designed the study is an idiot.

    I don’t mean to come off this way, but if there are any women that have heard of the tampons that were produced by p and g called “Rely” tampons, then you may also feel that this is not something that should be taken lightly. Rely tampons, for those who are not familiar, were an proprietary ultra absorbant tampon that ultimately contributed or was associated with an increased risk of what is known as “toxic shock syndrome.” It’s your body, you can do what you want with it, but at least talk to your doctor and see what they think and then make your own decision from there.

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  11. 11. Kvnptrck 1:02 pm 02/27/2012

    Edit: Should want to decrease their p-value* sorry

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  12. 12. Kate Clancy in reply to Kate Clancy 1:03 pm 02/27/2012

    Kvnptrck, I appreciate your candor on this. I hesitated to come out too strongly against the study because I do a lot of human subjects research and know how hard it is to get participants, particularly if you’re doing anything at all invasive. So I tend to criticize less on sample size and more on other issues. But I definitely hear you. For a study for something that is about to go to market, a consumer should be able to trust the company making the product, and expect a far higher sample size.

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  13. 13. Kvnptrck 1:21 pm 02/27/2012

    I think a more in depth study may be beneficial for everyone. If there are any women trying to conceive, it would be good to know if these decrease pH in the long term and if so to what extent, and the timing it takes for this decrease in pH to go back to “normal.” The increased acidity of the lady parts require a male’s ejaculate to be slightly basic (as in of higher pH or less acidic), so that all of the man’s “swimming team” can get to their destination efficiently. This is not to say any product is good or any product is bad, I am just saying that people having trouble conceiving should at least have some good data out there so that they can see if a change has any effects after removal and after menses.

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