An infected penis typically shows one or more clear signs: unusual redness or discoloration, swelling, discharge that isn’t normal for you, pain or burning during urination, sores or lesions, and a persistent foul smell. These symptoms can point to several different types of infection, from yeast overgrowth to bacterial infections to STIs, and each has its own pattern worth understanding.
Visible Changes to the Skin
The most obvious sign of infection is a change in how the skin looks. Redness, purple or gray discoloration, and swelling on the head of the penis are hallmarks of balanitis, which is a general term for inflammation of the glans. You might also notice shiny patches, areas where the skin looks white or waxy, or small sores and lesions. These changes tend to concentrate on the head of the penis and the area just beneath the foreskin, where moisture and warmth create a hospitable environment for bacteria and fungi.
Sores deserve close attention. Small, painful blisters or ulcers can indicate herpes, which typically appears 2 to 12 days after exposure, with an average of about 4 days. Firm, painless sores are more characteristic of syphilis. If you notice scaly, wart-like bumps, these could be genital warts caused by HPV. HPV warts often start as small, soft, dome-shaped bumps and can grow over time into larger, cauliflower-like clusters. They tend to appear on the frenulum, glans, inner foreskin, or the ridge around the head of the penis, and their color ranges from flesh-toned to pink, brown, or dark purple.
Normal Bumps vs. Signs of Infection
Not every bump is a problem. Two completely normal anatomical features frequently get mistaken for infections:
- Pearly penile papules are small, smooth, dome-shaped bumps (1 to 4 mm) that line up symmetrically in one or more rows around the corona, the ridge at the base of the glans. They’re uniform in size and shape, usually yellowish, white, or flesh-colored, and they don’t change over time. They’re most prominent on the top side of the corona and fade toward the frenulum.
- Fordyce spots are tiny (1 to 2 mm), creamy yellow, smooth papules on the glans or shaft. They become more visible during an erection or when the skin is stretched. Squeezing one may release a small amount of chalky white material. These are just visible oil glands.
The key differences from warts or infection: normal bumps are symmetrical, uniform in size, and don’t grow, spread, cluster irregularly, or cause any symptoms. Warts tend to vary in size, appear in irregular clusters, and can change shape over weeks or months.
Unusual Discharge
Some clear fluid at the tip of the penis during arousal is normal. What isn’t normal is discharge that appears on its own, especially if it has color, thickness, or odor. A white or frothy discharge, sometimes accompanied by blood in the urine, can signal a urinary tract infection. Gonorrhea often produces a thick, yellowish or greenish discharge, typically showing up within 2 to 8 days of exposure. Chlamydia may cause a thinner, more watery or milky discharge, usually appearing 1 to 3 weeks after exposure.
A thick discharge collecting under the foreskin, especially with bleeding around the foreskin, points to balanitis. If the discharge has a foul smell, that’s a strong signal that bacteria are involved and the situation needs medical attention.
Yeast Infection vs. Bacterial Infection
Men get yeast infections too, and they look different from bacterial ones. A penile yeast infection (fungal balanitis) typically causes moist skin on the penis, itching or burning, a thick white substance collecting in skin folds, and shiny white patches on the skin. The itching tends to be the dominant symptom, and the white buildup is often the giveaway.
Bacterial infections, by contrast, are more likely to produce colored discharge (yellow, green, or cloudy), a fishy smell, and more pronounced redness and swelling. A fishy odor in particular tends to point toward bacteria rather than yeast. Both types can cause discomfort and skin changes on the glans, which is why visual symptoms alone aren’t always enough to tell them apart. A doctor can usually distinguish the two with a quick exam or swab.
Pain and Burning
Where and when you feel pain narrows down the possibilities. Burning during urination is one of the most common signs of urethritis, an infection of the urethra (the tube that carries urine out through the penis). In men, painful urination is frequently caused by urethritis or prostate problems. Chlamydia and gonorrhea are the most common infectious causes of urethritis, but non-STI bacteria can trigger it too.
Soreness or tenderness concentrated on the head of the penis, especially with visible skin changes, is more typical of balanitis. Pain in the shaft or deeper in the pelvis can point to different issues entirely, including prostatitis. Sudden, severe pain with rapid swelling and discoloration is a red flag that warrants urgent care, as it could indicate a serious soft-tissue infection.
Smell as a Warning Sign
A mild, musky smell is normal, particularly after exercise or a long day. The genitals produce sweat, oils, and dead skin cells, and bacteria break these down into compounds that can smell sour or slightly cheesy. This is hygiene-related, not infection.
Smegma, the whitish or yellowish buildup that can accumulate under the foreskin, is a mix of oils, skin cells, sweat, and moisture. It’s not an infection itself, but because it’s moist, it creates an ideal breeding ground for bacteria. Regular cleaning resolves it. A smell that persists despite good hygiene is different. A fishy odor points to bacterial infection. A putrid, rotting smell is a medical emergency, as it can indicate a rare but dangerous condition called Fournier’s gangrene, where tissue begins to die rapidly.
How Quickly Symptoms Appear
If you’re concerned about a recent sexual encounter, the timeline matters. Symptoms don’t appear immediately. Gonorrhea typically shows up within 2 to 8 days but can take up to 2 weeks. Chlamydia takes 1 to 3 weeks on average. Herpes tends to appear faster, usually within 2 to 12 days. These are averages, and many STIs can be completely silent for weeks or even months. Chlamydia in particular is often asymptomatic in men, meaning you can carry and transmit it without any noticeable signs. If you’ve had a potential exposure, testing is more reliable than waiting for symptoms.
Signs That Need Prompt Attention
Most penile infections are treatable and not dangerous when caught early. But certain symptoms call for same-day medical care: an inability to urinate, high fever alongside genital symptoms, rapidly spreading redness or swelling, severe pain that comes on suddenly, bleeding from under the foreskin, or a foul rotting smell. Skin that looks dark, feels numb, or crackles when touched suggests tissue damage that requires emergency treatment.
For less urgent symptoms like mild redness, itching, slight discharge, or a new bump, scheduling a regular appointment within a few days is reasonable. A doctor can typically diagnose the type of infection with a physical exam and, if needed, a urine test or swab. Most infections clear up quickly with the right treatment, whether that’s an antifungal for yeast or antibiotics for bacteria.