Penile symptoms — discharge, burning when you pee, sores, or itching — most often point to chlamydia, gonorrhea, nongonococcal urethritis (NGU), genital herpes, or syphilis. But not every case is an STI: balanitis and plain irritation cause similar complaints. These overlap, and several are often silent, so only a test settles which one it is.
often silent; discharge or burning if anything
discharge and burning; can also hit throat/rectum
urethral discharge or burning with no gonorrhea found
painful blisters that crust over; tends to recur
| Item | Value |
|---|---|
| Chlamydia | curable — often silent; discharge or burning if anything |
| Gonorrhea | curable — discharge and burning; can also hit throat/rectum |
| Nongonococcal urethritis (NGU) | curable — urethral discharge or burning with no gonorrhea found |
| Genital herpes | managed — painful blisters that crust over; tends to recur |
Which STIs cause penile symptoms
Five conditions account for most STI-related penile symptoms in men. Each has a tell-tale pattern, but none is reliable enough to diagnose by sight.
Chlamydia
Chlamydia is caused by the bacterium Chlamydia trachomatis; most US genital infections come from serovars D–K CDC chlamydia. It's a quiet infection — about half of infected men have no symptoms at all. When symptoms do show, they usually appear within one to three weeks of exposure and look like NGU: a thin urethral discharge, burning on urination, sometimes urethral itching. Because it so often hides, a clear result after treatment matters; men who were positive should plan on retesting, which we cover under chlamydia reinfection.
Gonorrhea
Gonorrhea is caused by Neisseria gonorrhoeae, which can infect the genitals, rectum, and throat About Gonorrhea. In men it tends to announce itself: burning when urinating and a white, yellow, or green penile discharge that's often thicker and more obviously purulent than the chlamydia/NGU type. Less commonly it causes swollen, painful testicles — a sign of epididymitis (inflammation of the coiled tube behind the testicle that stores sperm, which can threaten fertility if untreated). A NAAT confirms it; see gonorrhea test for how those results read.
Nongonococcal urethritis (NGU)
NGU is urethritis that is not caused by gonorrhea, a syndrome rather than a single germ CDC urethritis Tx. Its causes include Chlamydia trachomatis, Mycoplasma genitalium, and sometimes Trichomonas, HSV, or adenovirus; in roughly half of cases no organism is ever identified. It presents mainly in men, with a mucoid or purulent urethral discharge, painful urination, and urethral itching, though some infections cause nothing. Treatment depends on the suspected cause; we walk through it in ngu treatment.
Genital herpes
Genital herpes is caused by two viruses, HSV-1 and HSV-2 About Herpes. Most people have no or very mild symptoms and never know they carry it; the majority of HSV-2 infections go undiagnosed. A first outbreak is the loudest: small blisters that break into painful sores on or around the genitals, rectum, or mouth, taking a week or more to heal, sometimes with fever, body aches, and swollen glands. Later outbreaks are shorter and milder, and many people feel a prodrome — a tingle, itch, or ache — before sores appear. Pain plus a blister-to-sore progression separates herpes from the painless sore of syphilis. For ongoing management options, see alternative herpes treatments.
Syphilis
Syphilis is caused by the bacterium Treponema pallidum and is curable with the right antibiotics About Syphilis. Its primary stage is one or more painless, firm, round sores called chancres at the site of infection — on the penis, anus, rectum, lips, or mouth. The chancre appears about three weeks after exposure (the incubation range runs ten to ninety days), lasts three to six weeks, and heals on its own whether or not you're treated. A vanishing sore is dangerous, not reassuring. If untreated, syphilis can advance to a secondary stage: a rough red or reddish-brown rash that can show on the palms and soles or the body, mucous-membrane lesions, fever, swollen lymph nodes, sore throat, patchy hair loss, headache, weight loss, muscle aches, and fatigue. Screening is also a pregnancy issue; see syphilis in pregnancy.
When it's not an STI
Not every penile symptom is an infection you caught from a partner. Balanitis — inflammation of the head of the penis, often with redness, soreness, and itching under the foreskin — is a common culprit, frequently driven by yeast overgrowth, poor or excessive washing, or skin conditions rather than an STI. Simple irritation from soaps, friction, latex, or spermicides can mimic the burning and redness of urethritis. None of these are reasons to skip testing, but they are reasons not to assume the worst before you have a result.
How to tell them apart
You can group most cases by their leading symptom, but these conditions overlap too much to tell apart by sight, and several are frequently silent. A test is what settles which one it is, if any.
- Discharge: A thicker, white-yellow-green discharge leans gonorrhea; a thinner, mucoid one leans chlamydia or NGU. The two overlap and need a lab to separate.
- A sore: A single painless, firm sore points to syphilis; clustered painful blisters or ulcers point to herpes.
- Burning without discharge: Often early urethritis (chlamydia, NGU, or gonorrhea), but irritation and balanitis can feel the same.
- No symptoms at all: Common with chlamydia, gonorrhea in some, and herpes, so screening beats waiting for a sign.
| Condition | Typical penile sign | Pain? | Often silent? | Confirming test |
|---|---|---|---|---|
| Chlamydia | Thin discharge, burning urination | Mild burning | Yes (about half of men) | NAAT |
| Gonorrhea | White/yellow/green discharge | Burning urination | Sometimes | NAAT |
| NGU | Mucoid or purulent discharge, itching | Painful urination | Sometimes | Urethritis evidence + NAAT |
| Herpes | Painful blisters → sores | Yes, painful | Yes (most undiagnosed) | Swab NAAT or culture |
| Syphilis | Single firm, painless sore (chancre) | Painless | Sore can be missed | Two serologic tests |
How it's tested
For chlamydia and gonorrhea, a NAAT on a urine sample is the preferred method; gonorrhea NAAT sensitivity usually runs above 90% with specificity near 99% CDC gonorrhea. NGU requires objective evidence of urethritis (Gram stain or first-void urine white-cell criteria) plus NAATs for chlamydia and gonorrhea CDC STI Tx 2021. Herpes is confirmed by swabbing an active lesion for type-specific NAAT or culture CDC herpes testing. Syphilis needs two serologic tests — a nontreponemal test (RPR or VDRL) and a treponemal test (such as TP-PA, FTA-ABS, EIA, or CIA) CDC syphilis lab 2024. In practice that means a urine sample, a self-collected swab, or a quick exam depending on what's suspected, free or low-cost at health departments, Planned Parenthood, and Title X clinics, with results usually back in a few days. Start at get tested, and if you're counting days since a hookup, check when to test after exposure.
What to do next
Overlapping symptoms are why you usually can't self-diagnose this; a test turns a guess into an answer. Get tested before assuming, hold off on sex until you have results and any prescribed treatment is complete, and tell recent partners so they can be checked. Antibiotics cure chlamydia, gonorrhea, NGU, and syphilis. Herpes is managed, not cured, with medication that shortens and reduces outbreaks.
Red flags — when to get seen urgently
- A swollen, painful testicle — possible epididymitis (inflammation of the tube behind the testicle that can affect fertility).
- Fever, severe pain, or a spreading rash on the palms or soles, which can signal advancing syphilis.
- Sores that won't heal, are widespread, or come with trouble urinating.
- Any symptom during pregnancy in a partner — untreated syphilis can be passed to the baby and needs urgent care.
- Discharge or sores plus systemic illness (chills, body aches, swollen glands) — get seen rather than waiting it out.