Most STIs in men show up as sores, bumps, rashes, or unusual discharge from the penis, but the specific appearance varies widely depending on the infection. Some STIs produce dramatic, unmistakable symptoms. Others look so subtle they’re easy to miss or confuse with normal skin variations. Here’s what each common STI actually looks like and how to tell them apart.
Sores and Blisters
Genital Herpes
Herpes typically appears as a cluster of small blisters on or around the penis, scrotum, or anus. The blisters are fluid-filled and often painful. Within a few days they rupture into shallow, open ulcers that may ooze or bleed, then slowly crust over with scabs as they heal. The entire cycle from blister to healed skin usually takes two to four weeks during a first outbreak.
A first herpes outbreak is almost always the worst. You may also notice flu-like symptoms: body aches, swollen lymph nodes in the groin, and fever. Future outbreaks tend to be milder, with fewer and smaller sores that heal faster. Symptoms first appear about 2 to 12 days after exposure, with 4 days being the average.
Syphilis
Primary syphilis produces a single, round, firm sore called a chancre, most often on the head of the penis. It’s usually painless, which is why many men don’t notice it. The sore has a clean, smooth base and raised edges. It appears anywhere from 10 to 90 days after exposure (21 days on average) and heals on its own within a few weeks, even without treatment.
That healing is deceptive. If untreated, syphilis progresses to its secondary stage, which produces a rash that can spread across the torso, arms, legs, and notably the palms of the hands and soles of the feet. This rash is typically rough, reddish-brown, and doesn’t itch. Rashes on the palms and soles are uncommon with most other conditions, so this pattern is a strong signal of syphilis. You might also develop flat, wart-like growths in the groin or around the anus during this stage.
Bumps and Growths
Genital Warts (HPV)
Genital warts appear as small, skin-colored bumps on the penis, scrotum, groin, or around the anus. They can be flat or raised. When several warts cluster together, they create a bumpy, cauliflower-like texture that’s one of the most recognizable STI signs. Some warts are so small and flat they’re nearly invisible. Warts can take anywhere from 3 weeks to many months to show up after exposure, making it difficult to trace when infection occurred.
Genital warts don’t usually hurt or itch, though some men notice mild irritation. They vary in size from pinhead-small to several millimeters across, and they can appear as a single bump or in groups.
Molluscum Contagiosum
Molluscum produces raised, round, skin-colored bumps that are firm and smooth with a distinctive small dent or dimple in the center. That central dimple is the key feature that sets molluscum apart from other bumps. The bumps typically appear in the groin, lower abdomen, inner thighs, or on the genitals. They’re painless and usually 2 to 5 millimeters across. Symptoms can take anywhere from 2 weeks to 6 months to appear after skin-to-skin contact.
Discharge and Urinary Symptoms
Chlamydia and gonorrhea are the two most common STIs that cause penile discharge, and they look different from each other. Gonorrhea typically produces a thick, yellowish or greenish discharge that may stain underwear. It often comes with a burning sensation during urination. Symptoms usually appear within 2 to 8 days of exposure, though it can take up to 2 weeks.
Chlamydia discharge tends to be thinner and more watery, sometimes clear or slightly cloudy. It’s generally less dramatic than gonorrhea discharge, and many men produce so little that they only notice a slight dampness or staining. Chlamydia symptoms appear within 1 to 3 weeks on average, but the infection frequently causes no visible symptoms at all. Up to half of men with chlamydia never notice anything unusual, which is why it spreads so easily.
Both infections can also cause redness or swelling at the opening of the penis.
STIs With No Visible Signs
Several important STIs produce no visible symptoms in men, at least not for a long time. HIV may cause a brief flu-like illness with body aches and fever within 1 to 2 weeks of infection, but there’s nothing to see on the skin during early stages. After that, the virus can remain silent for months or years. Hepatitis B and C also rarely produce visible genital symptoms; their effects are internal, primarily targeting the liver, and may not cause noticeable illness for weeks to months after exposure.
Trichomoniasis, a parasitic infection, causes symptoms in only about 30% of infected men. When it does, you might notice mild discharge, slight burning after urination or ejaculation, or irritation at the tip of the penis. Symptoms appear 5 to 28 days after exposure.
Normal Skin Variations That Mimic STIs
Not every bump on the genitals is an STI. Two very common, completely harmless conditions cause unnecessary panic.
Pearly penile papules are tiny, smooth, dome-shaped bumps that form a ring around the ridge (corona) of the penis head. They’re uniform in size, evenly spaced, and don’t change over time. Unlike genital warts, they follow a neat, symmetrical pattern and don’t cluster into cauliflower-like shapes. They’re a normal anatomical feature found in roughly 15 to 25% of men and require no treatment.
Fordyce spots are small, slightly raised bumps that look white, yellowish, pale red, or skin-colored. They’re typically 1 to 3 millimeters across, about the size of a sesame seed or smaller. These are simply enlarged oil glands that appear on hairless skin, commonly along the shaft of the penis or on the inner foreskin. They may appear individually or in clusters of 50 or more. They’re completely harmless and not sexually transmitted.
The key differences: Fordyce spots are very small, uniform, and unchanging. Pearly papules form a tidy ring. Genital warts, by contrast, tend to appear in irregular groupings, vary in size, and may grow or multiply over time.
When Symptoms Overlap
One of the tricky things about identifying STIs visually is that many symptoms overlap. A painless bump could be an early wart, a molluscum lesion, or a syphilis chancre. A small cluster of sores could be herpes or an irritated skin condition. Discharge could point to gonorrhea, chlamydia, or even a non-STI urinary tract infection.
Visual appearance alone is not reliable enough to identify which STI you’re dealing with. Even experienced clinicians rely on lab testing rather than visual assessment to make a diagnosis. If you notice any new sores, bumps, rashes, or discharge, testing is the only way to know for certain what’s going on. Many clinics offer rapid testing for the most common infections, with results available within a few days.
It’s also worth remembering that having one STI doesn’t rule out having another. Co-infections are common, particularly with chlamydia and gonorrhea, which frequently occur together.