A women's normal vaginal pH ranges between 3.8 and 4.51 which means the vagina is acidic. This acidity helps to keep it healthy. pH is a measure of how acidic or alkaline something is. The pH range goes from 1 which is highly acidic to pH14 which is highly alkaline. pH 7 is neutral.
Lemon juice is acidic and has a pH of 2.4, whilst household bleach is highly alkaline at 12.5. Pure water is pH 7. (Values taken from Wiki)
Note that many soaps have a pH value of 9-10 so that too thorough washing will upset the healthy acidic environment of the vagina. Many experts advise not using soap on this area, and certainly try not to get soap inside which will alter the vaginal pH. The vagina is a self-cleansing organ and all you need to do is wash away secretions trapped around the external folds.
The average pH of semen ranges from 7.2 to 7.8 which explains why sex sometimes makes a woman more prone to infections such as BV.
Blood has a pH range of from 7.34 to 7.45 which explains why menstruation can cause an attack of BV. Research has shown that menstrual blood has the effect of neutralizing the normally acidic vagina - not a desirable things for any woman prone to infections.
pH values will change as you progress through life. Pre-puberty the reading will be around pH7; during our reproductive years when the vagina is more vulnerable to infection an acidic pH of around 3.8 to 4.5 guards our health; and after menopause we return to a pH of 6-7.
You can buy a kit to test yourself at home Vagisil Screening Kit however many women find it does not give them the definitive answer they wanted.
Some women have found that by taking a swab using a cotton tip aplicator and then transferring it to pH paper they could get a good reading.
Hold the swab between thumb and forefinger, insert and then rotate both clockwise and anticlockewise whilst trying to touch both walls of the vagina. Then place the swap on a pH strip and compare.
Very important to use pH testing paper that covers the appropriate range. What you need is one that covers the 3.3 to 5 range such as this one. Hydrion Ph Paper Range 3.0 - 5.5 Single Roll Dispenser - this is the pH range that was used in the research that showed that women could get a result almost as good as a doctor in measuring their own pH.
These strips cover only the important midrange reading - it will be clear if you are off one end.
When doctors took pH readings from different sites within the vagina the readings did not vary very much so don't stress if you're not sure exactly where the swab is touching..
The oral capsules in Fem Dophilus, although not designed to alter pH, do sometimes alter the level as they help your normal protective bacteria reestablish themselves.
A Portugese study of 990 healthy women3 found certain factors were associated with higher vaginal pH (that's what you don't want). They were age, BMI, sexual intercourse without barrier contraception, dryness and irritation symptoms. Now you can't do much about age but some of the others are within a woman's control.
Factors associated with a lower pH (what you do want) were physical activity, being employed and hormone replacement therapy.
This article on Cytolytic Vaginosis is essential reading for women who would like to alter the pH balance in the vagina towards more alkaline.
It is said that bathing in sea water can alter vaginal pH. It is possible to make your own "sea water" by adding sea salt to ordinary tap water. The sea salt adds the sodium and other minerals from the sea and the ordinary tap water adds minerals such as calcium.
To do this, measure the tap water into a sitz bath. Let it stand for ten minutes. Then add 35 grams of sea salt per liter of water or approximately 4 ounces of sea salt per gallon of water and stir it into the water until disolved. Sitting in this will have a similar effect to bathing in seawater.
There appear to be no scientific studies that prove that sea water can alter the vaginal pH but certainly there is anecdotal evidence that it does.
A woman with BV will usually have a reading higher than pH4.5 which means that the area is more alkaline than it should be. With the high pH of semen, it takes several hours for the normal acidic vaginal pH to return after sexual intercourse.1 This acidity is one of conditions that protects the vagina from infection so that this period of alkalinity leaves a woman vulnerable to bacterial infection after sex. Using a condom is a sensible precaution if you're prone to chronic bacterial vaginosis.
Again, a pH test will reveal an alkaline reading for the vagina. It can increase from around a pH of 4 up to a highly alkaline 7. This alkaline environment happens as the usual lactobacillus are killed off and it creates a more favorable "home" for the protozoa that causes trich. This is another infection where the presence of semen can allow pathogenic bacteria to gain the upper hand.
During a woman's period, the blood makes for a doubably favorable environment - firstly, the blood enables the trich protozoa to reproduce at a faster rate and, secondly, it increases their ability to adhere to the wallls fo the vagina.
Yeast infection does not normally give that characteristic increase in vaginal alkalinity so that the pH will usually be 4.5 or less. Some women wonder can semen cause yeast infection and although it doesn't directly, an allergy to semen (which some women have) can give a vaginal discharge and signs very similar to vaginal yeast infection.
A pH reading alone can not accurately diagnose ANY vaginal infection. It is simply one of the indicators.
Since 1990, the US has allowed over-the-counter sales of vaginal antifungal medicines for yeast infection and it is believed that if women used a standard pH test it would reduce incorrect treatment by over 50%.
1. Smith KPB. Estrogens and the urogenital tract. Studies on steroid hormone receptors and a clinical study on a new estradiol releasing vaginal ring. Acta Obstet Gynecol Scand 1993;72(Suppl 157):S1?26
2. Boskey ER, and Cone RA, Whaley KJ, Moench TR. Origins of vaginal acidity: high D/L lactate ratio is consistent with bacteria being the primary source. Hum Reprod. 2001 Sep;16(9):1809—13.
3. Pereira Da Silva D, Martinez De Oliveira J, Negreiro F. Observational study of vaginal pH in healthy Portuguese women. Minerva Ginecol. 2011 Apr;63(2):203—12.