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