A yeast infection is an overgrowth of a fungus called Candida, most commonly Candida albicans, on or inside the body. About 75% of women will have at least one vaginal yeast infection in their lifetime, and 40% to 45% will have two or more episodes. While vaginal yeast infections are the most well-known type, Candida can also cause infections in the mouth, throat, skin folds, and on the penis.
What Happens Inside Your Body
Candida naturally lives on your skin and inside your body, including the vagina, mouth, and gut. In small amounts, it’s harmless. Your immune system and the bacteria that share these spaces keep the fungus in check. The problem starts when something disrupts that balance and Candida gets the opportunity to multiply.
When Candida shifts from a passive state to an aggressive one, it changes shape. It transforms from round yeast cells into long, thread-like filaments that can physically penetrate tissue. In this form, the fungus produces enzymes that break down cells, adheres more effectively to surfaces, and can form protective clusters called biofilms that make it harder to clear. This is why a yeast infection causes visible irritation and damage to the affected area, not just discomfort.
Common Causes and Risk Factors
The vagina maintains its own ecosystem. A group of bacteria called Lactobacillus keeps the environment slightly acidic, with a healthy pH between 3.8 and 4.5. That acidity discourages Candida from growing out of control. Anything that weakens those protective bacteria or changes that acidic environment can open the door to a yeast infection.
Antibiotics are one of the most common triggers. Broad-spectrum antibiotics, the kind prescribed for sinus infections or bronchitis, don’t distinguish between harmful bacteria and beneficial ones. When they wipe out Lactobacillus along with the targeted infection, the vagina becomes less acidic, and yeast thrives in the more neutral environment.
High blood sugar is another significant risk factor. Candida uses glucose as a preferred energy source, so elevated sugar levels in tissue give the fungus more fuel to grow. High glucose also enhances Candida’s ability to stick to cells, invade tissue, and shift into its more aggressive filament form. This is why people with poorly controlled type 2 diabetes are more prone to yeast infections.
Other common risk factors include:
- Hormonal changes: pregnancy, birth control pills, and hormone therapy all alter the vaginal environment
- A weakened immune system: from conditions like HIV or medications that suppress immune function
- Moisture and heat: tight clothing, wet swimsuits, and non-breathable underwear create conditions Candida favors
Symptoms of a Vaginal Yeast Infection
The hallmark symptom is intense itching in and around the vagina. This is often accompanied by a thick, white discharge that looks like cottage cheese and has little to no odor. The lack of a strong smell is one of the key differences between a yeast infection and bacterial vaginosis, which typically produces a noticeable fishy odor.
Other common symptoms include burning during urination, pain during sex, redness and swelling of the vulva, and soreness in the vaginal area. Symptoms can range from mild itching to severe discomfort that disrupts daily life. Not every yeast infection looks the same, and some people experience only one or two of these symptoms.
Yeast Infections in Men
Men can get yeast infections too, though it happens less frequently. The infection typically develops on the head of the penis, causing a condition called balanitis. Symptoms include a red, itchy rash (often in patches), burning and irritation around the head of the penis and under the foreskin, and swelling. Men may also notice a thick, white cottage cheese-like discharge, difficulty pulling back the foreskin, or shiny sores on the penis. After the infection clears, the skin may peel or become flaky as it heals.
Uncircumcised men are at higher risk because the warm, moist environment under the foreskin is favorable for Candida growth. Sexual transmission is possible but not the primary cause. Most male yeast infections develop from the same triggers as vaginal ones: antibiotics, high blood sugar, or a compromised immune system.
How Yeast Infections Are Diagnosed
If you’ve had a yeast infection before and recognize the symptoms, you may feel comfortable treating it with an over-the-counter product. But if it’s your first time experiencing these symptoms, or if they don’t match the typical pattern, getting a proper diagnosis matters. Bacterial vaginosis, certain sexually transmitted infections, and other conditions can cause similar itching and discharge.
A healthcare provider will typically do a pelvic exam and may take a swab of vaginal discharge to examine under a microscope or send to a lab. One useful clue is vaginal pH. Yeast infections generally don’t raise pH above the normal 3.8 to 4.5 range, while bacterial vaginosis pushes it above 4.5. This simple test helps distinguish between the two, since their treatments are completely different.
Treatment Options
Most uncomplicated yeast infections respond well to antifungal medications, which are available both over the counter and by prescription. Over-the-counter options come as creams, ointments, or suppositories that you insert vaginally. Treatment courses typically range from one to seven days depending on the product strength.
For people who prefer a single-dose option, a prescription oral antifungal tablet is the standard alternative. One pill, taken once, resolves most uncomplicated infections within a few days, though symptoms sometimes take up to a week to fully clear. If you’re still experiencing symptoms after completing treatment, that’s a sign the infection may not actually be caused by yeast, and it’s worth getting tested.
Recurrent yeast infections, generally defined as four or more episodes in a single year, require a different approach. Treatment usually involves a longer initial course of antifungal medication followed by a maintenance regimen to prevent the infection from coming back.
Reducing Your Risk
Because yeast infections stem from an imbalance in the body’s natural microbial environment, prevention focuses on keeping that balance intact. Wearing breathable cotton underwear, changing out of wet clothing promptly, and avoiding douches or scented products in the vaginal area all help maintain a healthy environment. If you have diabetes, keeping blood sugar well controlled directly reduces Candida’s ability to grow and invade tissue.
Probiotics have drawn interest as a prevention strategy, particularly for people with recurrent infections. Lactobacillus rhamnosus is the most researched strain for vaginal health and has been shown to help kill yeast and restore the vaginal bacterial balance in people with a history of yeast infections. Lactobacillus crispatus is another strain with clinical evidence supporting its role in vaginal health. These won’t treat an active infection, but they may help prevent future episodes when taken regularly.
If you’re taking antibiotics for another condition and you’re prone to yeast infections, let your provider know. In some cases, a preventive antifungal can be prescribed alongside the antibiotic course to head off the predictable disruption to your vaginal flora.