Green discharge is almost always a sign of infection. In women, the most common causes are trichomoniasis, gonorrhea, and bacterial vaginosis. In men, green or yellow-green discharge from the penis typically points to gonorrhea or another form of urethritis. While the shade of green can range from faint yellow-green to distinctly green, any discharge with a green tint warrants testing rather than a wait-and-see approach.
Trichomoniasis
Trichomoniasis is one of the most common sexually transmitted infections worldwide, and green discharge is one of its hallmark signs. The infection is caused by a parasite passed during unprotected sex. Discharge from trichomoniasis can be thin or frothy and ranges from clear to white, yellowish, or greenish, often with a noticeable fishy smell. You may also experience itching, burning, redness, or discomfort when urinating.
What makes trichomoniasis tricky is that about 70% of people with the infection have no symptoms at all. That means you can carry and transmit it without ever noticing a change in discharge. When symptoms do appear, they can show up anywhere from a few days to a month after exposure. The infection is easily curable with a short course of oral antibiotics, and sexual partners need treatment at the same time to prevent reinfection.
Gonorrhea
Gonorrhea is another STI closely associated with green discharge, especially in men. Penile discharge from gonorrhea is typically white, yellow, or green and may appear thick or pus-like. It often shows up within a few days of exposure, along with burning during urination.
In women, gonorrhea can cause increased vaginal discharge that may look yellowish or greenish, but many women have mild or no symptoms at all. That’s a problem, because untreated gonorrhea is one of the leading preventable causes of pelvic inflammatory disease (PID). PID can permanently damage the fallopian tubes, uterus, and surrounding tissues, potentially leading to infertility. About 10 to 15% of women with untreated chlamydia develop PID, and gonorrhea carries similar risks. Testing is straightforward: a urine sample or swab is all that’s needed, and the infection responds well to antibiotics when caught early.
Bacterial Vaginosis
Bacterial vaginosis (BV) isn’t an STI, but it’s one of the most common vaginal infections in women of reproductive age. It happens when the balance of bacteria in the vagina shifts, allowing certain types to overgrow. The discharge from BV is usually thin and grayish-white, but it can sometimes take on a greenish tint. A strong fishy odor, especially after sex, is the most recognizable feature.
BV can develop after douching, using new soap or body wash near the vaginal area, or sometimes without any obvious trigger. A healthy vaginal pH sits between 3.8 and 4.5, and BV pushes that pH higher, creating an environment where problematic bacteria thrive. BV is treatable with antibiotics, but it has a tendency to recur.
Retained Tampon or Foreign Object
A forgotten tampon or other object left in the vagina can cause discharge that turns yellow, green, pink, gray, or brown. The smell is often the first thing people notice: it’s distinctly foul and gets worse the longer the object stays in place. This happens because bacteria multiply rapidly in the warm, moist environment around the retained object.
If you suspect a retained tampon, try to remove it gently yourself. If you can’t reach it or the smell and discharge persist after removal, get it removed by a healthcare provider. The main serious risk is toxic shock syndrome, which is very rare but can be life-threatening. Fever, dizziness, or a rash after a retained tampon warrants immediate medical attention.
Urethritis in Men
For men, green or yellow-green discharge from the penis is a clear sign of urethritis, which is inflammation of the urethra. Gonorrhea is the most common cause, but when gonorrhea testing comes back negative, the condition is classified as nongonococcal urethritis. Chlamydia accounts for 15 to 40% of those cases, with other bacteria and sometimes no identifiable cause making up the rest.
The discharge can range from thin and mucus-like to thick and pus-like. It may appear only in the morning or leave stains on underwear throughout the day. Burning or stinging during urination and itching at the tip of the penis are common accompanying symptoms. Some men have visible discharge on examination without feeling any symptoms at all, which is why screening matters if a partner has been diagnosed with an STI.
How to Tell What’s Causing It
Color alone doesn’t give you a definitive diagnosis. Trichomoniasis, gonorrhea, BV, and retained foreign objects can all produce greenish discharge, and the overlap in symptoms is significant. What helps narrow things down is the combination of features:
- Frothy, fishy-smelling discharge with genital irritation leans toward trichomoniasis.
- Thick, pus-like discharge (especially from the penis) suggests gonorrhea.
- Thin, fishy-smelling discharge without much irritation is more consistent with BV.
- Extremely foul-smelling discharge that came on suddenly raises the possibility of a retained object.
The only way to know for sure is testing. STI panels using urine samples or swabs are fast and widely available. Most clinics can test for gonorrhea, chlamydia, and trichomoniasis simultaneously. BV is typically diagnosed through a pelvic exam and a sample of the discharge. If you’re sexually active and notice green discharge for the first time, getting a full STI screen rather than testing for just one infection gives you the clearest picture.
Why Prompt Treatment Matters
All of the infections behind green discharge are treatable, most with a short course of antibiotics. But the consequences of leaving them untreated can be serious. Gonorrhea and chlamydia can lead to PID in women, which causes permanent damage to reproductive organs and is a major preventable cause of infertility. In men, untreated urethritis can spread to the testicles, causing pain, swelling, and in rare cases fertility problems.
Trichomoniasis, while less likely to cause structural damage, increases susceptibility to other STIs, including HIV. It can also cause complications during pregnancy, including preterm delivery and low birth weight. Treatment is simple and effective, but both partners need to be treated at the same time. Having sex before both partners finish treatment is the most common reason these infections bounce back.