Anyone who has ever experienced PMS is aware of how changes in hormone levels can affect our bodies. But in addition to making you feel extra [insert emotion] the week before your period, hormone fluctuations can cause a host of other symptoms—and in some cases, contribute to the development of vaginal infections.

Hormones are a part of the endocrine system, and act as chemical messengers that help cells speak to each other. They influence almost every organ in the body

When it comes to vaginal health, hormones play a role by:

So how can you tell whether your vaginal itchiness is because you’ve been washing out your vagina with a perfumed gel (for the record, don’t do this!) or due to a shift in hormone levels? 

Read on to learn how to better understand how hormones influence your vaginal symptoms.

Hormones and the Vaginal Microbiome 

Shifts in hormone levels can alter the vaginal environment—and in some cases, make it more susceptible to infection. 

The role of estrogen in vaginal infections

Estrogen promotes the production of a sugar called glycogen. Glycogen causes the lining of the vagina to thicken and acts as the main form of sustenance for protective bacteria called lactobacilli. When there is less estrogen present, there is less glycogen, and therefore fewer lactobacilli to maintain a healthy vaginal pH and keep “bad” bacteria at bay. This presents an opportunity for BV-causing bacteria to overgrow. 

But while too little estrogen can catalyze BV, too much estrogen can actually encourage a yeast infection.

A vaginal yeast infection happens when a type of fungus called Candida—which naturally lives on the skin and in the vagina—overgrows, producing an itching and burning sensation around the vagina, not to mention the infamous “cottage cheese” discharge.

Recent studies have found that the presence of estrogen causes Candida to grow differently and causes changes in yeast gene expression. These changes all help Candida grow and can even help it escape detection by the host immune response, which means, if Candida is present in your Vaginal Microbiome, it will likely turn intoyeast infections when estrogen is present in high amounts.

Cyclical hormones and fertility 

As our hormones change throughout the month, as well as when we get pregnant, give birth, and go through menopause, the risk of bacterial or yeast infections change. This also happens when switching birth controls or dealing with a hormonal condition or imbalance. If you are managing consistent or recurring hormonal changes, vaginal issues may follow suit.

Menstruation and the vaginal microbiome 

Lastly, menstruation itself affects the vaginal environment. Vaginal pH is naturally acidic and considered ‘normal’ between 3.8 and 4.5 on the pH scale. Since blood has a pH of 7.4, during your period, vaginal pH is usually higher and more alkaline. If you have an especially long or heavy period, this can create an environment that allows certain pathogens to multiply.

TL;DR: there are lots of ways these hormones and the microbiome can overlap. If you want to go one step further than education, try testing your vaginal microbiome over time with Evvy. Understanding how your microbiome looks at different points in your menstrual cycle or fertility journey can show you any changes in the composition of your vaginal bacteria and fungi!

FAQs on vaginal infections and hormones 

Can estrogen cause BV?

Nope! Healthy levels of the estrogen can actually have a protective effect against BV. This is because estrogen promotes the production of glycogen, which feeds protective vaginal bacteria called lactobacilli. In fact, BV is more commonly reported at the start of the menstrual cycle, when estrogen levels are at their lowest! 

This concept doesn’t only apply to BV. This decline in estrogen, and therefore lactobacilli, can also increase the risk of aerobic vaginitis, another bacterial vaginal infection, as well.  

Can estrogen increase my risk of a yeast infection?

Yes — high estrogen is associated with yeast infections, which is thought to be why they are so prevalent during pregnancy, when estrogen levels can increase around 30-fold. Yeast infection symptoms also tend to appear during the luteal phase (just before you get your period), due to the surge of estrogen at ovulation.

Can estrogen affect UTIs?

By now you’ve probably memorized the general relationship between estrogen and lactobacilli: 

  • If estrogen decreases, then lactobacilli decreases  — and that equals a vaginal microbiome more susceptible to infection
  • If estrogen increases, then lactobacilli increases — and that equals a vaginal microbiome less susceptible to infection

UTIs are primarily caused by the notorious bacteria Escherichia coli (aka E. coli) invading the vaginal microbiome, which, you guessed it, means that less estrogen makes you more prone to getting a UTI. 

Another estrogen-related reason people can be more prone to UTIs has to do with estrogen’s relationship to the vaginal lining. Estrogen causes the vaginal lining to thicken.  If estrogen levels are low, the vagina can become thin and dry, a condition known as vaginal atrophy. Vaginal atrophy not only increases the risk of getting a UTI because thinner tissue is more prone to infection, but it may also contribute to pelvic organ prolapse, which is when an organ within the pelvis slips from its usual position into the vagina. 

This explains why UTIs are more prevalent during menopause and postmenopause, when estrogen levels are much lower. 

The 411 on hormonal conditions and vaginal infections 

There are some key conditions that are helpful for all people with periods to know about. We’ve unpacked how they relate to the vaginal microbiome here:


Pain during sex, period pain, and pain when peeing can be a sign of endometriosis, a condition where tissue that mimics the lining of the womb (endometrium) grows elsewhere in the body. 

Research on endometriosis and the vaginal microbiome is extremely limited, so the relationship between the two remains to be determined. However, we sometimes see members of the Evvy community mistaking symptoms of endometriosis with those of a vaginal infection. 

Unfortunately, like many conditions people with wombs experience, diagnosing endometriosis can be difficult. The gold standard to confirm that you have endometriosis is to undergo exploratory surgery, though doctors often treat endo based on symptom presentation. 

Endo symptoms are typically cyclical and can get significantly worse right before and during your period. If this sounds like you, it’s a good idea to get checked out by your doctor and bring up your concerns about endometriosis during the appointment. 

Functional Hypothalamic Amenorrhea

Functional hypothalamic amenorrhea (say that five times fast) is the scientific name for missing periods due to an energy deficit

People with functional hypothalamic amenorrhea lose their menstrual cycle due to an imbalance in the amount of calories they are burning compared to the calories they are consuming. Without enough energy, the body cannot produce an adequate amount of hormones—including estrogen—which, as you now know, is crucial for vaginal health, especially when it comes to producing lactobacilli. 

This puts those with functional hypothalamic amenorrhea at an increased risk for developing vaginal infections such as bacterial vaginosis, aerobic vaginitis, and other forms of dysbiosis. Thankfully, this can be remedied by increasing caloric intake. If you have missing periods, talk to your doctor about whether or not functional hypothalamic amenorrhea may be at the root of the issue.

Polycystic ovarian syndrome (PCOS) 

Polycystic ovarian syndrome (PCOS) is another condition rooted in hormonal dysfunction. Again, the research on direct relationships between the vaginal microbiome and PCOS is largely unknown. 

However, we do know that people with PCOS have abnormally high levels of androgen hormones (i.e. testosterone), which can disrupt the balance of hormones that regulate the menstrual cycle and prevent ovulation. This disruption leads to lower levels of estrogen, which may increase the risk of vaginal dysbiosis.

Like endometriosis, there’s no definitive test for PCOS, but your doctor would be able to conduct a symptom assessment for diagnosis. Some PCOS symptoms to look out for are abnormal body hair growth (formally known as hirsutism), missing periods, thinning and hair loss from the head, and acne. 

How do I know if hormones are what’s actually causing my vaginal symptoms? 

A telltale sign that hormones are contributing to your infection is whether your symptoms are cyclical—that is, they change in line with your menstrual cycle. If your infection has come along just as your estrogen levels have started to shift for another reason, such as being pregnant or starting hormonal contraception, this could also be a sign that it’s hormonal. 

Sometimes, hormone fluctuations can cause symptoms that aren’t related to an infection at all, but could be mistaken for one. The main example of this is dryness, and its BFF, pain during sex which can lead many individuals to believe they have an infection. 

Evvy’s Vaginal Health Test will be able to tell you whether any infection-related bacteria or fungi are present down there—and if there are none, hormones could be a source of your symptoms.

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