Abnormal Vaginal Discharge and STDs: Which Infections Cause It?

Clinically reviewed by Dr. Pipat Finn, M.D., Senior Doctor, Doctor Pattaya. Last reviewed: August 2026

You noticed something different this morning. Maybe it started a few days after unprotected sex, and now you are sitting in your hotel room somewhere between Jomtien and Walking Street, Googling symptoms instead of enjoying the beach. That is exactly why this article exists. Abnormal discharge is one of the most common reasons people walk into our clinic, and most of the time we can sort it out the same day.

The tricky part is this: the way discharge looks or smells can give us clues, but it cannot give us a diagnosis. Chlamydia, gonorrhea, trichomoniasis, bacterial vaginosis, and less well-known infections like Mycoplasma genitalium all cause discharge. Some people have no symptoms at all, which is why so many infections get missed. If something feels off, get tested. Do not wait and hope it clears up on its own.

Normal Discharge vs Abnormal Discharge — What You Are Looking For

Normal vaginal discharge is clear or white, has little to no odour, and shifts slightly throughout your cycle. That is your body doing its job. Abnormal discharge looks or smells different: the colour has changed, the smell is unfamiliar, the texture is off, or the amount has increased for no clear reason.

The warning signs worth acting on are yellow, green, grey, or frothy discharge, a strong or unfamiliar smell, and discharge that comes with itching, burning, pain during sex, or pain when urinating. Any of those, especially after a new partner or unprotected sex, warrants a check.

In men, any discharge from the penis other than urine or semen is abnormal, full stop. A clear drip first thing in the morning, a white or yellow discharge, or anything streaky in your underwear should not be there. Get it looked at.

Which STDs Cause Abnormal Discharge — and What They Look Like

Chlamydia

Chlamydia is one of the most common infections we test for, and also one of the sneakiest. Most people with chlamydia have no discharge at all. When there is discharge, it tends to be white or cloudy, sometimes with a mild odour. In women, the infection often sits on the cervix, which means nothing visible appears even when the infection is active.

In men, chlamydia can produce a clear or milky discharge from the tip of the penis, often most noticeable first thing in the morning. Burning when urinating is common. Left untreated, it can cause urethritis in men and pelvic inflammatory disease in women.

Gonorrhea

Gonorrhea tends to be louder than chlamydia. The discharge is usually thicker, yellow or yellowish-green, and harder to miss. In women it often comes from the cervix. In men there is typically a cloudy or yellow discharge from the penis, often with pain when urinating.

Something that matters specifically in this part of the world: gonorrhea is becoming harder to treat. Antibiotic-resistant strains are a real problem across Southeast Asia, and Thailand has documented higher resistance rates than many Western countries. Standard antibiotics from five years ago may not work now. We use current local data to guide what we prescribe, which is exactly why you want a proper clinical assessment rather than a pharmacy guess.

Trichomoniasis

Trichomoniasis is caused by a tiny parasite rather than a bacterium. In women it produces some of the most distinctive discharge: often frothy, yellow-green, and with a strong unpleasant smell. Itching and redness are common alongside it. In men, trichomoniasis usually causes no symptoms at all, though some notice a mild clear discharge or irritation.

It is completely curable with the right medication. The problem is that most people do not know they have it.

Bacterial Vaginosis

Bacterial vaginosis, or BV, is not always sexually transmitted, but it is frequently triggered by sex and worth covering here. The discharge is typically grey or off-white, thin, and has a distinctive fishy smell that becomes stronger after sex. It does not usually cause itching or soreness.

BV happens when the natural bacterial balance in the vagina is disrupted. It is common and very treatable, but it can raise your risk of catching other STDs, so it should not be brushed aside.

Abnormal Discharge in Men — Urethral Discharge and What Causes It

Male patients often come in unsure whether what they have noticed is actually a symptom. It is. Any penile discharge that is not urine or semen needs assessment.

The most common causes are gonorrhea and chlamydia. Trichomoniasis is less frequent in men but does occur. Non-gonococcal urethritis, or NGU, is a broad term for urethral inflammation not caused by gonorrhea. Chlamydia is often responsible, but Mycoplasma genitalium accounts for a significant share of cases too.

The discharge in NGU tends to be clear or milky rather than yellow, and mild enough that some men only notice it after a full night’s sleep. Do not dismiss a small amount as nothing. A swab or urine test takes minutes.

Lesser-Known Infections That Also Cause Discharge — Mycoplasma Genitalium and NGU

Mycoplasma genitalium does not get talked about enough. It causes inflammation of the urethra in men and the cervix in women. The discharge is usually mild. Patients who come in with persistent discharge after a negative standard STI panel often turn out to have this.

The issue is that Mycoplasma genitalium is not on every standard testing panel, and it has its own antibiotic resistance problems. Usual chlamydia treatment does not always clear it. If you have already been treated for an STD but the discharge has not resolved, tell us. We test for it specifically and treat it with the right regimen.

Ureaplasma is a related organism that can cause similar symptoms and is also missed by standard testing. If results come back negative but something still feels wrong, a broader workup is what you need.

Why Discharge Colour Alone Cannot Tell You What Infection You Have

A colour guide is a useful starting point, and nothing more. The same shade of yellow can come from gonorrhea, chlamydia, or a non-infectious cause. Frothy green discharge points toward trichomoniasis, but not every case looks like a textbook photo. And some of the most common STDs produce little to no discharge at all.

WHO and CDC guidelines both make this clear: you cannot accurately identify the cause of discharge from symptoms alone. Swabs, urine tests, and sometimes blood tests are needed. Trying to match your discharge to a colour chart and then picking up antibiotics at a pharmacy is not a safe approach, especially given antibiotic-resistant gonorrhea in this region. A proper test is always worth it. Our STD treatment page covers which infections cause discharge and how each is managed.

Symptoms That Should Not Be Ignored Alongside Discharge

Discharge on its own is one signal. Pain during sex can indicate infection has spread to the cervix or deeper pelvic structures. Pelvic pain, lower abdominal cramping, or pain in the testicles in men can all suggest the infection is progressing.

Burning when urinating is very common with gonorrhea and chlamydia in both sexes. Swollen lymph nodes in the groin, sores, or blistering alongside discharge can point toward a co-infection, meaning more than one STD at the same time. Co-infections are not rare, especially after higher-risk sexual encounters.

If you have pelvic pain, fever, or feel genuinely unwell alongside discharge symptoms, do not wait. Pelvic inflammatory disease and testicular infection need prompt treatment to avoid long-term complications.

How Doctors Diagnose the Cause of Abnormal Discharge

When you come in, we take a brief history: what you have noticed, when it started, recent sexual partners. This is completely confidential. We have heard everything, and we are not here to lecture anyone.

Then we collect samples. For women this is usually a swab from the cervix or vagina. For men it is often a first-catch urine sample and sometimes a urethral swab. We may also check vaginal pH and look at the discharge under a microscope. These quick checks help guide immediate treatment while full lab results are being processed.

Most standard STI results come back within one to two days. If clinical signs strongly suggest gonorrhea or chlamydia, we may start treatment on the same visit and adjust based on results. Mycoplasma genitalium testing takes a little longer but is available here.

What to Expect at Doctor Pattaya — From Walk-In to Treatment

No appointment needed. Walk in any time. For tourists who are leaving in two days, that matters more than anything else.

You will be seen privately in a proper consultation room. We will ask a few questions, take the relevant samples, and explain what we are testing for and why. If results confirm an infection, we prescribe the right medication and go through dosing with you clearly. For gonorrhea, we follow current Thai treatment guidelines rather than older regimens, given resistance patterns in this region.

We also cover partner notification. If you test positive, your partner should be told and tested. This is not about blame. It is about stopping an infection from going in circles. We can advise you on how to handle that conversation if you need us to.

Doctor Pattaya sees tourists, expats, and residents from Jomtien, Naklua, Pratumnak, and across the wider area. For anyone staying at a hotel who cannot travel easily, doctor hotel visits are available across Pattaya and the surrounding areas. You can also read more about STD testing and treatment options at our clinic if you want to know what to expect before you come in.