Penile symptoms — discharge, burning when you pee, sores, itching, or rash — are most often caused by chlamydia, gonorrhea, nongonococcal urethritis (NGU), genital herpes, or syphilis. Non-STI causes like balanitis and simple irritation can look identical. These overlap, and several are often silent, so a test tells you which one it is.
Chlamydia trachomatis
Neisseria gonorrhoeae
Urethritis not caused by gonorrhea
Herpes simplex virus
| Item | Value |
|---|---|
| Chlamydia | curable — Chlamydia trachomatis |
| Gonorrhea | curable — Neisseria gonorrhoeae |
| Nongonococcal urethritis (NGU) | curable — Urethritis not caused by gonorrhea |
| Genital herpes | managed — Herpes simplex virus |
Which STIs cause penile symptoms?
A handful of infections account for most STI-related penile complaints. Each has a typical pattern, but none is reliable enough to diagnose by eye. The pattern guides testing without replacing it.
Chlamydia
Chlamydia is caused by the bacterium Chlamydia trachomatis, and most US genital infections involve serovars D–K CDC chlamydia fact sheet. It's a quiet infection: roughly half of infected men have no symptoms at all. When symptoms do show up, they usually appear within one to three weeks of exposure and look like mild urethritis — a thin discharge, discomfort or burning when urinating, sometimes irritation at the tip of the penis. The subtlety helps it spread. Learn more on the chlamydia overview.
Gonorrhea
Gonorrhea, caused by Neisseria gonorrhoeae, can infect the genitals, rectum, and throat CDC, About Gonorrhea. In men it tends to be louder than chlamydia: burning on urination and a penile discharge that is often white, yellow, or green. Less commonly it causes swollen, painful testicles, a sign the infection has tracked back into the epididymis, the coiled tube behind the testicle that stores sperm, which can threaten fertility if untreated. A discharge that's thicker and more colored leans gonococcal, though only a test confirms it. See the gonorrhea page for the full picture.
Nongonococcal urethritis (NGU)
NGU is urethritis — inflammation of the urethra — that isn't caused by gonorrhea. It's a syndrome rather than a single bug: Chlamydia trachomatis, Mycoplasma genitalium, and sometimes Trichomonas, HSV, or adenovirus can all trigger it, and about half of cases never have an organism identified CDC STI Treatment Guidelines, 2021. It mainly affects men and presents as urethral discharge that may be mucoid or purulent, painful urination, and urethral itching. Some men have no symptoms. People often wonder whether it clears on its own — see can ngu go away on its own without treatment?
Genital herpes
Genital herpes is caused by two viruses, herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) CDC, About Genital Herpes. Most people have no symptoms or very mild ones, and the majority of HSV-2 infections are never diagnosed. When a first outbreak does occur, it produces blisters that break open into painful sores, often with flu-like symptoms — fever, body aches, and swollen glands. The sores can appear on or around the genitals, rectum, or mouth and take a week or more to heal. Later outbreaks are shorter and milder, and many people get a warning prodrome of tingling or itching beforehand. If you're managing recurrences, see alternative herpes treatments.
Syphilis
Syphilis is caused by the bacterium Treponema pallidum and is curable with the right antibiotics CDC, About Syphilis. Its hallmark is the primary chancre: one or more painless, firm, round sores at the spot where the bacteria entered — on the penis, anus, lips, or mouth. The chancre appears about three weeks after exposure (the incubation window runs ten to ninety days) and heals on its own in three to six weeks whether or not it's treated, even though the infection hasn't gone anywhere. Weeks later the secondary stage can bring a rough red or reddish-brown rash, classically on the palms and soles, along with fever, swollen lymph nodes, sore throat, patchy hair loss, and fatigue. Read what is syphilis? causes, stages & risks for the staged progression.
When it's not an STI
Plenty of penile symptoms have nothing to do with an infection passed during sex. Balanitis — inflammation of the head of the penis — can cause redness, soreness, discharge, and itching, and it's often driven by yeast, poor drying under the foreskin, or skin irritation rather than an STI. Simple irritation from soaps, lubricants, friction, or tight clothing produces similar redness and burning. They can mimic an STI closely enough that you can't sort them out yourself.
How to tell them apart
Clinicians lean on a few discriminating features, while keeping in mind that all of them overlap. Discharge with burning urination points toward urethritis — gonorrhea, chlamydia, or NGU — with thicker, colored discharge nudging toward gonorrhea and thinner discharge toward chlamydia or NGU. A sore changes the question. A painful blistery cluster suggests herpes, while a single painless firm sore suggests a syphilis chancre. Redness and itching under the foreskin with no urethral discharge points away from an STI and toward balanitis or irritation.
These patterns overlap too much to tell apart by sight alone, and several — chlamydia, gonorrhea in some men, and herpes especially — are frequently silent. A test settles which one it is, if any. You usually can't self-diagnose.
Penile-symptom causes at a glance
| Cause | Typical penile signs | Sore? | Often silent? |
|---|---|---|---|
| Chlamydia | Thin discharge, mild burning on urination, appears 1–3 weeks after exposure | No | Yes — about half of men |
| Gonorrhea | White/yellow/green discharge, burning urination, sometimes swollen painful testicle | No | Sometimes |
| NGU | Mucoid or purulent discharge, painful urination, urethral itching | No | Sometimes |
| Genital herpes | Painful blisters that break into sores; possible fever and swollen glands | Yes — painful | Yes — most go undiagnosed |
| Syphilis | Single firm, round sore; later a rash on palms/soles and body | Yes — painless | Yes — chancre heals on its own |
| Balanitis / irritation | Redness, soreness, itching under the foreskin or at the tip | No | No |
How penile symptoms are tested
Testing is usually quick and depends on what's suspected: a urine sample or self-collected swab for chlamydia and gonorrhea by NAAT — the recommended method for both CDC STI Treatment Guidelines, 2021 — a swab of any sore for herpes by NAAT or culture, and two blood tests (a nontreponemal plus a treponemal test) to confirm syphilis. NGU is diagnosed by showing objective evidence of urethral inflammation, then testing for the underlying organisms. You can get tested at a health department, Planned Parenthood, or Title X clinic — often free or low-cost, with results usually back in a few days. If you're unsure how long to wait after a possible exposure, check when to test after exposure.
What to do next
Don't wait for symptoms to disappear on their own. The syphilis chancre and even chlamydia can quiet down while the infection persists. Get tested for the panel that fits your exposure, hold off on sex until you have answers, and let recent partners know if a test comes back positive. Most of these infections are curable or manageable with standard treatment once identified.
Red flags — when to get seen urgently
- A swollen, painful, or tender testicle, which can signal infection tracking into the epididymis and needs prompt care.
- Fever, severe pelvic or abdominal pain, or feeling systemically ill alongside genital symptoms.
- A painless firm sore — a possible syphilis chancre — even if it later heals on its own.
- A widespread rash, especially on the palms and soles, with fever or swollen lymph nodes.
- Inability to urinate, or sores so painful that urinating becomes impossible.
- Any new sore or discharge in a newborn's parent or during pregnancy — get evaluated quickly.