Several sexually transmitted infections can cause vulvar swelling, but the most common culprits are trichomoniasis, genital herpes, gonorrhea, and syphilis. Each one causes swelling through a different mechanism, and the accompanying symptoms can help you figure out what you might be dealing with before you get tested.
Trichomoniasis
Trichomoniasis is one of the most frequent STI causes of vulvar inflammation. It’s caused by a parasite rather than a bacterium or virus, and when it produces symptoms, they range from mild irritation to severe swelling and redness of the vulva. You may also notice itching, burning, discomfort when peeing, and a thin discharge that’s clear, white, yellowish, or greenish with a fishy smell. Many people with trichomoniasis have no symptoms at all, which is why it often goes undiagnosed and untreated for long stretches.
The swelling from trichomoniasis tends to be diffuse, meaning it affects the vulvar tissue broadly rather than creating a single lump or sore. Treatment is a course of oral antibiotics taken twice daily for seven days, and symptoms typically start improving within a few days of starting treatment.
Genital Herpes
A first outbreak of genital herpes (HSV-2, and sometimes HSV-1) can cause significant vulvar swelling alongside its more recognizable symptoms. The outbreak usually starts 2 to 12 days after exposure. Small bumps or blisters appear around the genitals, which then rupture into painful ulcers that ooze or bleed. The surrounding tissue often becomes inflamed and swollen in response.
What sets a primary herpes outbreak apart is that it frequently comes with flu-like symptoms: fatigue, body aches, fever, and swollen lymph nodes in the groin. The combination of painful sores, general swelling, and feeling systemically unwell is a fairly distinctive pattern. Recurrent outbreaks tend to be milder, with less swelling and fewer or smaller sores.
Gonorrhea and Bartholin’s Gland Abscesses
Gonorrhea deserves special attention because of its link to Bartholin’s gland abscesses, which cause a very specific type of vulvar swelling. The Bartholin’s glands sit on either side of the vaginal opening and produce lubricating fluid. When one of these glands gets infected or blocked, it can form a cyst or abscess that creates a noticeable, often painful lump on one side of the vulva.
Research published in PubMed found that 10% of patients with a Bartholin’s cyst or abscess tested positive for gonorrhea, compared with just 3% of those without one. On further analysis, gonorrhea infection was associated with more than five times the odds of having a Bartholin’s abscess. This link was strong enough that the study’s authors recommended routine gonorrhea testing for anyone who shows up with this type of swelling. Chlamydia and trichomoniasis were also found in patients with Bartholin’s abscesses, though their statistical link wasn’t as strong.
A Bartholin’s abscess typically appears as a tender, warm lump on one side of the vulva, usually near the vaginal opening. It can grow to the size of a golf ball and may make sitting or walking uncomfortable. If you notice one-sided swelling in this area, it’s worth getting tested for gonorrhea and chlamydia even if you don’t have other obvious STI symptoms.
Syphilis
Primary syphilis causes a firm, round, painless ulcer called a chancre at the site where the bacterium entered the body. In women, this can appear on the vulva, though it sometimes develops on the cervix where it goes completely unnoticed. The chancre itself may cause some localized swelling, and up to 80% of people with primary syphilis develop swollen lymph nodes in the groin, which are typically painless and rubbery.
The painlessness is the key feature here. If you have vulvar swelling with a firm ulcer that doesn’t hurt, syphilis should be on your radar. The chancre heals on its own within a few weeks even without treatment, but the infection progresses to more serious stages if left untreated.
Lymphogranuloma Venereum
This is a rarer cause, but it’s worth knowing about because it can cause dramatic, long-lasting vulvar swelling. Lymphogranuloma venereum (LGV) is caused by specific strains of the same bacterium responsible for chlamydia, but it behaves very differently. Instead of staying in the genital tissues, it invades the lymphatic system.
LGV progresses through three stages. In the third stage, chronic inflammation and scarring of the lymphatic channels can block lymph drainage from the vulva, leading to persistent, sometimes severe swelling. In extreme cases this produces what’s called vulvar elephantiasis, where the tissue becomes permanently thickened. Treatment cures the infection and stops further damage, but scarring that’s already occurred may be permanent. LGV is uncommon in the U.S. and Western Europe but occurs more frequently in parts of Africa, Southeast Asia, and Central America.
How STI Swelling Differs From Other Causes
Vulvar swelling isn’t always caused by an STI, and the accompanying symptoms can help you distinguish between possibilities. A yeast infection causes intense itching and a thick, white, cottage cheese-like discharge, and while it can cause some redness and swelling, the itching is usually the dominant complaint. Bacterial vaginosis produces a grayish-white discharge with a strong fishy odor but generally doesn’t cause significant swelling on its own.
STI-related swelling tends to come with additional clues: unusual discharge color (greenish or yellowish with trichomoniasis), visible sores or blisters (herpes), a painless lump on one side (Bartholin’s abscess from gonorrhea), or a painless firm ulcer (syphilis). If swelling appeared after a new sexual contact, STI testing is the most direct way to get answers.
Getting Tested
Vaginal swab tests for chlamydia and gonorrhea are highly accurate, with detection rates ranging from about 64% to 100% for vaginal specimens depending on the specific test used. These tests work by detecting the genetic material of the bacteria, so they can identify infections even when symptoms are minimal. Your provider will likely test for multiple STIs at once, since co-infections are common. Blood tests are used for syphilis and herpes, while trichomoniasis can be detected through a vaginal swab.
Managing Swelling While You Wait for Results
If your vulva is swollen and uncomfortable while you’re waiting for test results or for treatment to take effect, a sitz bath can help reduce pain and swelling. Fill a bathtub with 3 to 4 inches of warm water (around 104°F) and soak for 15 to 20 minutes. Plain warm water is all you need. Epsom salts, oils, and other additives can actually irritate inflamed tissue. Pat the area dry afterward with a clean towel rather than rubbing. You can repeat this three to four times a day if it’s providing relief.
Wearing loose, breathable cotton underwear and avoiding scented products in the area will also help minimize irritation while the underlying cause is being addressed.
Signs That Need Urgent Attention
Most STI-related vulvar swelling resolves with appropriate treatment, but certain symptoms signal a more serious situation. Fever above 100.5°F, swelling that’s spreading rapidly, intense pain that seems out of proportion to what you see, or skin that looks darkened or feels crackly to the touch are all red flags. Vulvar cellulitis can, in rare cases, progress to a dangerous deep-tissue infection that requires emergency treatment. If swelling is worsening quickly and you’re feeling increasingly unwell, that warrants a same-day medical visit rather than waiting for a scheduled appointment.