Vaginal infections develop when something disrupts the natural balance of bacteria and yeast that normally live in the vagina. That balance is more delicate than most people realize, and a surprisingly wide range of everyday factors can tip it: antibiotics, hormonal shifts, sexual activity, clothing choices, and certain hygiene products. Understanding what keeps the vagina healthy makes it much easier to see how infections take hold.
How the Vagina Protects Itself
A healthy vagina isn’t sterile. It’s home to a community of beneficial bacteria, primarily Lactobacillus species, that produce lactic acid and keep the environment acidic. The average vaginal pH when these bacteria are thriving sits around 3.5, roughly as acidic as orange juice. At that pH, lactic acid becomes a potent natural antimicrobial, killing off harmful bacteria, fungi, and parasites before they can multiply.
When something reduces the Lactobacillus population or raises the pH, the door opens for other organisms to take over. That’s the core mechanism behind nearly every type of vaginal infection.
Bacterial Vaginosis: A Shift in Bacteria
Bacterial vaginosis (BV) is the most common vaginal infection among women of reproductive age, affecting roughly 23 to 29 percent globally. It happens when harmful bacteria outgrow the protective Lactobacillus, raising the vaginal pH and producing symptoms like thin white or gray discharge with a noticeable fishy smell.
Several things increase the risk of this bacterial shift. Douching is one of the biggest culprits, because it physically flushes out beneficial bacteria. Having a new sexual partner or multiple partners also raises BV risk, likely because exposure to different genital bacteria can alter the vaginal environment. Not using condoms is another factor. BV is not considered a sexually transmitted infection, but sexual activity clearly plays a role in triggering it.
Yeast Infections: Fungal Overgrowth
Candida, a type of yeast, lives in small amounts in the vagina without causing problems. A yeast infection happens when something allows Candida to multiply faster than the body can keep it in check. The hallmark symptom is thick, white, cottage cheese-like discharge, usually accompanied by itching and irritation.
The single most common trigger is antibiotic use. Broad-spectrum antibiotics don’t just kill the bacteria causing your illness. They also wipe out Lactobacillus, making the vagina less acidic and giving yeast an environment where it can thrive. This is why many women develop a yeast infection a few days into a course of antibiotics.
Other risk factors include pregnancy, hormonal birth control, diabetes (because elevated blood sugar feeds yeast growth), and a weakened immune system. Steroids and chemotherapy also increase susceptibility by suppressing the body’s ability to control Candida.
Sexually Transmitted Infections
Some vaginal infections are passed directly from one person to another during sex. Trichomoniasis is caused by a parasite that spreads through penis-to-vagina, vagina-to-penis, or vagina-to-vagina contact. It typically infects the lower genital tract and produces green, yellow, or gray discharge that can look frothy or bubbly. People with trichomoniasis can pass it to partners even when they have no symptoms at all.
Chlamydia and gonorrhea, both bacterial STIs, can also cause vaginal symptoms including cloudy, yellow, or green discharge. These infections require different treatment than BV or yeast infections, which is one reason getting the right diagnosis matters before trying to treat symptoms at home.
Hormonal Changes and Infection Risk
Estrogen plays a direct role in keeping the vaginal walls thick, lubricated, and hospitable to Lactobacillus. When estrogen drops, the tissue becomes thinner and drier, and the bacterial community can shift in ways that invite infection.
This is why certain life stages carry higher infection risk. During menopause, estrogen levels fall permanently, which can lead to a condition called atrophic vaginitis: chronic irritation and inflammation from thinning tissue. Breastfeeding temporarily suppresses estrogen and can have similar effects. Pregnancy, on the other hand, raises estrogen but also alters immune function, making women more susceptible to both yeast infections and BV during those months.
Hygiene Products That Do More Harm Than Good
The vagina is self-cleaning, and many products marketed as vaginal hygiene aids actually cause the problems they claim to prevent. Douching, which typically involves flushing the vagina with a mixture of water, vinegar, baking soda, or fragrances, strips away protective bacteria and disrupts pH balance. It’s one of the most well-established risk factors for BV.
Scented body washes, feminine sprays, powders, and wipes can cause similar problems. The fragrances and chemicals irritate vaginal tissue and can alter the bacterial environment. Warm water and a gentle, unscented soap on the external area is all that’s needed. Anything that goes inside the vaginal canal is introducing a foreign substance that can trigger irritation and bacterial imbalance.
Clothing and Moisture Buildup
Yeast thrives in warm, moist environments, and your underwear choice can either help or hurt. Synthetic fabrics like nylon and spandex trap heat and moisture against the skin, creating conditions that encourage fungal growth. Cotton is breathable and absorbent, which helps keep the area drier and less hospitable to yeast.
If you exercise in synthetic workout clothes, changing out of them promptly makes a difference. Sleeping without underwear is another simple way to let the area breathe and prevent moisture from accumulating overnight. For workouts specifically, lightweight moisture-wicking polyester worn with a cotton liner can help manage sweat without trapping it.
How to Tell Which Infection You Have
The type of discharge is often the most useful clue, though it’s not a perfect diagnostic tool on its own.
- Yeast infection: thick, white, cottage cheese-like discharge with itching and no strong odor
- Bacterial vaginosis: thin, white or gray discharge with a fishy smell
- Trichomoniasis: green, yellow, or gray discharge that may be frothy or bubbly
- Chlamydia or gonorrhea: cloudy, yellow, or green discharge, sometimes with pelvic pain
Many vaginal infections share overlapping symptoms, and some cause no noticeable symptoms at all. If you’ve never had a vaginal infection before, or if your symptoms don’t match a pattern you’ve experienced previously, getting tested gives you a clear answer and the right treatment. Treating a yeast infection when you actually have BV, or vice versa, can make the problem worse or mask an STI that needs specific medication.