Yeast infections are never fun but they are fairly common. Nearly 75 percent of women have had a yeast infection at least once in their lives, according to the CDC. About 40-45 percent of women will have two or more.(1)
It is important to realize that yeast also normally lives in the vagina, mouth and gastrointestinal tract but only in small amounts. Yeast normally lives in balance with other organisms in our body.
A yeast infection is an overgrowth of the fungus Candida. If there is too much yeast present, then symptoms appear. There is a balance that is needed to keep yeast levels in check.
In the vagina, yeast infection symptoms may include: pain on urination, swelling, redness, itching and a thick cottage cheese-looking discharge.
Yeast infections can be affected by menstruation for a number of reasons.
The factors involved include the hormone levels of estrogen and progesterone, sugar levels in the vaginal tissue, and the pH or the acidity of the vagina maintained by lactobacillus bacteria, a bacteria that is supposed to live in our vagina.
In the first half of your menstrual cycle, estrogen levels rise and glycogen (stored sugar) is produced and deposited in the cells in the vagina, which will provide nutrition for our good bacteria lactobacillus.
Lactobacilli produce lactic acid, which keep the vaginal pH more acidic at a pH of 4.0-4.5. Lactobacilli are responsible for keeping other organisms in the vagina from causing harm.
The second half of your cycle occurs after ovulation. Estrogen levels fall, as progesterone levels rise. Sugar is released from glycogen, which feeds the lactobacilli, but yeast are also able to feed on the sugar.
If an imbalance occurs between the amounts of lactobacilli and yeast, the yeast overgrows. This can lead to a yeast infection occuring before a woman’s period.
During menses, the pH of the blood is about 7.35, which is more alkaline than the normal pH of the vagina. Yeast can tolerate a swing in pH and survive.(5)
It may be that an overgrowth of yeast started before your menses, and afterwards the yeast was able to gain a stronger foothold.
1) Vulvovaginal Candidiasis. Centers for Disease Control and Prevention. Retrieved June 19, 2016.
2) Vaginal Microbiota. Evolmedwomenshealth. Retrieved June 19, 2016.
3) The Basics of Yeast Infections. How Stuff Works Health. Retrieved June 19, 2016.
4) YEAST INFECTION AND PERIOD. How Your Period and Yeast Infections Are Related. Candida Hub. Retrieved June 19, 2016.
5) Drake, S M et al. Vaginal ph and microflora related to yeast infections and treatment. Br J Vener Dis 1980;56:107-10.