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SciAmChem: Don’t douche, she declares acidly

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

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Frucht der Edelkastanie

Your vaguely suggestive image of chestnuts for the day.

In high school, I enjoyed participating in the science fair. I chose fairly random topics each year, but I do remember the year I studied the pH of soil and its impact on the color of flower petals. I grew a small set of African violets for a few weeks, then ground up their petals and subjected them to a spectrophotometer. Of course, with the small changes I made to the soil and short amount of time I changed the soil pH, I found no differences in petal color, but I felt like a Real Scientist.



What I do these days is Real Science, of course, but no one told me you could study hormones and the uterus and call it Science when I was in high school. So when I asked around about how I could contribute to Scientific American’s Chemistry Day, and someone suggested I look into vaginal pH and its impact on yeast infections, my interest was piqued.

You probably know that pH is how you measure how acid or basic a solution is. And you may even remember that water is considered neutral, at a pH of about 7 along the 0 to 14 pH scale. But did anyone tell you that the vagina is acidic?

Healthy, premenopausal vaginal pH tends to range from about 3.8-4.5. (However, this may be a bit US or Euro-centric. A topic for a whole other blog post would be to examine global variation in pH: I found an article on Indonesian women that suggests a slightly higher average: Ocviyanti et al 2010.) Having an acidic vagina is a good thing, because it makes the vaginal and uterine environment less hospitable to bacteria and other foreign bodies. When the vagina is a bit more basic, say around 5 and up, it seems to be more susceptible to bacterial infections and yeast overgrowth.

A few things impact vaginal pH. First, it appears to correlate inversely with estradiol concentrations. Estradiol is the hormone that increases through the first half of the cycle and peaks at ovulation. This means estradiol is rather low from the premenstrual phase, through menses and the first week or so of the next cycle. So the vagina becomes a bit more basic during this time, as well as through perimenopause and menopause. In fact by menopause, vaginal pH nears neutral (Caillouette et al 1997).

As you might expect, putting things into your vagina with a higher pH can increase its pH as well. This is where unprotected heterosexual sex and douching come in. Semen is very slightly basic, with a pH of healthy ejaculate around 7.2-7.8. This means an acidic vaginal environment could be inhospitable to semen, but also that semen could increase vaginal pH.

To douche is to cleanse the vagina, usually with a stream of liquid. There are now also wipes available. Some, but not all, data suggest African-American women have different attitudes about douching than Caucasian women, and douche more frequently (Hansen Cottrell 2006).

Yet aside from its use as an insult (or, in the case of my roller derby team, a battle cry when a particular jammer is up), the term douche probably didn’t make it into regular conversation that often… until recently. Summer’s Eve, a brand of feminine cleaning products that includes douches and wipes, has gotten into some trouble with their most recent advertising campaign. Their talking hand ads portray racial stereotypes (and have since been pulled), and their historical ad, in the words of a recent feministing commenter, help remind women that to many we are just “a vagina with legs.”

With these videos, young and old alike (the extended version of the “historical” one played at the opening of Harry Potter) now have the impression that douching and feminine wipes are a way to show your vagina some love.

They are not.

A quick Google search turns up several reputable websites with good medical information, all of which recommend against douching. A quick Google Scholar search reveals empirical science articles that demonstrate at least two main reasons douching is unhealthy. First, many douching products are more basic than a healthy premenopausal vagina. Second, douching products and feminine wipes contain fragrance, which can irritate the sensitive skin of the labia, vulva and vagina.

Both of these issues serve to disrupt normal vaginal flora. And when you disrupt the normal flora, the benign bacteria who live in your body all the time and whose presence tends to outcompete the bad stuff, you get more of the bad stuff. This can lead to an increased risk of bacterial vaginosis (Brotman et al 2008, Holzman et al 2001) and yeast infections, and BV in particular can increase the risk of pre-term birth (Hillier et al 1995).

Now, some douche products claim to be pH-balanced, and Summer’s Eve is one of them. But I cannot find for the life of me what that actual pH is. Is it pH-balanced to skin (around 5.5)? Is it pH-balanced in that it is neutral (7)? Both of those would indicate that it is too alkaline for the vagina.

But even if we assume that feminine cleansing products are at a low enough pH to not disrupt the vagina’s acidity, you still have fragrance. And not only are a significant number of people now allergic to the main fragrances used in consumer products (Buckley et al 2001), fragrances can be inherently irritating to the skin around the genitals in those who aren’t allergic. Allergic reactions to fragrance can initiate or worsen vulvar disease (Margesson 2004).

Let your vagina clean itself. It is acidic for a reason, and no, it’s not supposed to smell like a flower. It’s supposed to smell like a vagina.


Brotman, R., Klebanoff, M., Nansel, T., Andrews, W., Schwebke, J., Zhang, J., Yu, K., Zenilman, J., & Scharfstein, D. (2008). A Longitudinal Study of Vaginal Douching and Bacterial Vaginosis–A Marginal Structural Modeling Analysis American Journal of Epidemiology, 168 (2), 188-196 DOI: 10.1093/aje/kwn103

Buckley, D., Wakelin, S., Seed, P., Holloway, D., Rycroft, R., White, I., & McFadden, J. (2000). The frequency of fragrance allergy in a patch-test population over a 17-year period British Journal of Dermatology, 142 (2), 279-283 DOI: 10.1046/j.1365-2133.2000.03298.x

Caillouette JC, Sharp CF Jr, Zimmerman GJ, & Roy S (1997). Vaginal pH as a marker for bacterial pathogens and menopausal status. American journal of obstetrics and gynecology, 176 (6) PMID: 9215184

Cottrell, B. (2003). Vaginal Douching Journal of Obstetric, Gynecologic, and Neonatal Nursing, 32 (1), 12-18 DOI: 10.1177/0884217502239796

Hillier, S., Nugent, R., Eschenbach, D., Krohn, M., Gibbs, R., Martin, D., Cotch, M., Edelman, R., Pastorek, J., Rao, A., McNellis, D., Regan, J., Carey, J., & Klebanoff, M. (1995). Association between Bacterial Vaginosis and Preterm Delivery of a Low-Birth-Weight Infant New England Journal of Medicine, 333 (26), 1737-1742 DOI: 10.1056/NEJM199512283332604

Holzman, C., Leventhal, J., Qiu, H., Jones, N., & Wang, J. (2001). Factors Linked to Bacterial Vaginosis in Nonpregnant Women American Journal of Public Health, 91 (10), 1664-1670 DOI: 10.2105/AJPH.91.10.1664

Margesson, L. (2004). Contact dermatitis of the vulva Dermatologic Therapy, 17 (1), 20-27 DOI: 10.1111/j.1396-0296.2004.04003.x

Ocviyanti, D, Rosana, Y, Arifin, Z, & Darmawan, F (2010). Effect of contraception on vaginal acidity among Indonesian women Indonesian Journal of Obstetrics and Gynecology, 34 (2), 69-72

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. rusalka 12:54 pm 08/2/2011

    If douches are pH-balanced (and even if the meaning is uncertain, it seems clear that this means they have a pH of 7 or lower), and semen has a pH of >7, why isn’t unprotected vaginal sex riskier for the vaginal flora than douching? What happens to semen in the vagina? How does the vagina get back to its normal acidity after sex (or douching, for that matter)? I’m not trying to support douching – I agree, there is no justification for making women think their vaginas need to smell like flowers – I would just like more explanation!

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  2. 2. Alex Wild 1:15 pm 08/2/2011

    Bonus points for roller derby reference!

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  3. 3. kclancy 1:21 pm 08/2/2011

    rusalka – thanks for writing. I have the same question! I’m unclear what the mechanism is to restore the acidic environment, and I’m unclear how negative the association is with unprotected sex. I wonder if frequency, mechanism of contact (active wiping or douching as opposed to, you know, ejaculation) and fragrance (since it turns out fragrance is a major ingredient of douches and is a major irritant) might explain why douching could be worse than unprotected sex when it comes to disruption of vaginal flora.

    Alex, I thought you would appreciate that! Hooooooouuuuuuche!!!!!

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  4. 4. rusalka 3:49 pm 08/2/2011

    Thanks for the reply!

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  5. 5. Gaythia 4:31 pm 08/2/2011

    I think that the questions raised in the comments above indicate that it would be good to get some input here from a gynecologist or medical biologist on this subject.

    On the cultural side, I think it would be interesting to learn why females in certain communities are more prone to douche. Does this really imply a desire to smell like flowers? Or does lack of access to effective means of reproduction and disease control, combined with advertising that promotes a vague idea of being “clean down there” still lead to using douching in the hopes that it will help?

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  6. 6. kclancy 5:07 pm 08/2/2011

    rusalka, you’re very welcome — that’s the whole fun of having a blog!

    Gaythia, I am a human evolutionary biologist, I just don’t happen to be a specialist in the study of vaginal pH. I mostly focus on the endometrium. The fun of writing a blog is writing at the limits of my knowledge and enjoying the interaction with commenters as they carry the conversation forward. As Bora recently said, most blog posts are not intended to be an explainer or a definitive answer, but the beginning of a conversation:

    As for the cultural question, the reading I have done so far suggests that the higher incidence of douching in some populations (which again, only some studies have found) does have to do with different cultural expectations, not to smell like flowers, but yes, to be “clean.” There may also be some incorrect ideas about contraception that are producing increased frequencies of douching in some populations. Interestingly, the incidence of bacterial vaginosis has been found to be higher in some samples of African-American populations compared to Caucasian samples. So either they have a higher incidence of BV which makes them think they need to douche to be clean, OR the douching itself is increasing their risk of BV… or both.

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  7. 7. akraft22 6:16 pm 08/2/2011

    Thank you for this post, Dr. Clancy. I have been waiting over 10 years for someone to explain to me some basics about the female body. (I’m 28 and I still get freaked out by vaginal discharge.) Please post more on the female body to help dispel the many myths that are out there and to help keep unsuspecting women away from useless products. Cheers.

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  8. 8. hanjeanwat 7:10 pm 08/2/2011

    I am so happy you wrote this, Kate! “The vagina is self-cleaning!” is my friend’s motto; it’s great to see you putting it out there.

    I’m really curious about the semen questions regarding evolution. Have vajayjays been evolving to be rid of excess sperm?

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  9. 9. Gaythia 7:17 pm 08/2/2011

    I agree, fostering an interactive conversation is the fun, and the value of blogging!

    Bora has done such a great job in organizing SA blogs. Perhaps that is what causes me to think of raising expectations as to how the SA blog network members as well as commenters could interact.

    Other commenters, such as Rusalca and akraft22 above are raising some interesting questions and issues. I hope that you have an opportunity to expand on this post.

    I am a little familiar with the history of douching and Lysol back in the 1920′s when it was definitely believed by many a birth control method (and birth control was illegal). I would assume that the history goes back further than that. And also some folk culture memories of this practice might continue.

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  10. 10. kclancy 10:24 am 08/3/2011

    Thanks akraft22, hanjeanwat and Gaythia. There are always more topics to blog than time to blog, but I certainly hope to expand on this topic in the future. I also hope more women take up the mantle with me to blog about these topics — we need a ladybusiness posse :) .

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  11. 11. voltaire 12:27 pm 08/4/2011

    I’d like to reply to rusalka’s original question about why unprotected vaginal sex is not as harmful as douching. You have to consider the volume of liquid entering the vagina. If memory and personal experience(!) serve me, the maximal ejaculate volume is around 10-20 ml or considerably less than one fluid ounce whereas for douching, the volume is one cup (8 oz) or more.
    In turn, a logical (but probably unethical) experiment would be to compare the effect on the vagina of a high number of ejaculations versus one ejaculation in a day.

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  12. 12. kclancy 4:09 pm 08/4/2011

    Great point, voltaire. And there would certainly be ethical ways to test this, by creating a solution the same pH as semen and testing its effects on vaginal pH when varying the volume.

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  13. 13. Tony61 10:59 am 08/5/2011

    Excellent topic and I agree with Voltaire’s answer about volume of ejaculate versus douche– I’m sure a chemist could figure out the stoichiometry.

    The thing that gives the fishy odor that some find disagreeable is the presence of amines by anaerobic bacteria. The lactobacilli species that normally inhabit the vagina are odorless and produce lactic acid which lowers the pH. When Gardnerella vaginalis overgrows, the pH rises and anaerobic species overgrow. The anaerobes produces various amines that smell like fish, and we call this Bacterial Vaginosis.

    Some small epidemiologic studies* show that African-American women are more prone to gardnerella colonization which may answer the question as to why there are cultural differences in douching practice. Why is gardnerella more prevalent in African-American women? Don’t know.

    The proper way to diagnose odor is to to do a couple tests. One is the “whiff test”: place a drop of vaginal fluid on a slide with a drop of KOH (potassium hydroxide, a very strong base) to release the amines. A positive test is marked by a strong fishy odor and suggests BV. There are also color slides on the market that turn color with amines. The second test is to look at the vaginal secretions under a microscope and look for clumps of small bacterial cells on the large vaginal squamous cells. These are called “clue cells” and should be present on less than 20% of the vaginal squames.

    Proper treatment of BV is with a selective antibiotic that will kill only anaerobes and gardneralla and leave the normal lactobacilli intact, usually metronidazole or clindamycin. Douching is not as selective and can disrupt the normal flora.

    *Payne SC, Cromer PR, Stanek MK, Palmer AA. Evidence of African-American women’s frustrations with chronic recurrent bacterial vaginosis. J Am Acad Nurse Pract. Feb 2010;22(2):101-8. [Medline]

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  14. 14. voltaire 7:25 pm 08/5/2011

    In reply to Tony61, “why is gardnerella more prevalent in African American women?”, I don’t have an answer but I do have a hypothesis. Back in my graduate studies in microbiology, I learned that the baby’s normal flora was established after passage through the birth canal. Therefore if the mother has gardnerella, the chances are high that the baby will also have gardnerella – an example of generational transfer which leads to the cultural practice of douching for each infected generation. As I said, a hypothesis only.

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  15. 15. kclancy 5:06 pm 08/12/2011

    Tony61, great citation, thanks.

    Voltaire, that is both an interesting and testable hypothesis!

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  16. 16. rachelbobco 8:37 pm 09/30/2011

    Wow! I knew the vajajay was self cleaning; little did I know there is ‘normal vaginal flora’ !!!! fantastic! That is something I’m going to bring up the next time I feel the need to badger my GF into bringing me flowers. :) (I’m going to phrase it like, well I bring some vaginal flora whenever I visit, doll. You need to cough up the roses already!)

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  17. 17. dhbone 6:00 pm 02/25/2012

    Ruska, PH balanced does NOT mean neutral. Usually it means that it is balanced the opposite way to make up for an imbalance. For example, if you have hard water which is very basic, shampoo may be ph balanced–meaning more acidic–to make up for how basic the water is. But that doesn’t mean neutral 7 because human hair and skin is slightly acidic, so neutral wouldn’t necessarily be what it needs.

    Also, thanks to the writer for this article and thanks for not making awful, corny references to the vagina by using words like vajayjay and lady parts. It makes me feel so uncomfortable and it sounds truly stupid. So props for this well written, informative article that doesn’t talk about the vagina like it’s some secret embarrassing topic.

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  18. 18. Kate Clancy in reply to Kate Clancy 12:43 pm 02/27/2012

    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.

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