STIs can look very different depending on which infection is involved. Some cause blisters, others cause painless sores, and a few produce bumps that look like warts or pimples. Many STIs in men produce no visible symptoms at all, which is part of what makes them spread so easily. Here’s what each common STI actually looks like when it does show up.
Genital Herpes
Herpes typically starts with tingling or itching around the genitals or anus, lasting up to 24 hours before anything visible appears. Then a patch of red, swollen skin develops on the penis, scrotum, thighs, or buttocks. Small fluid-filled blisters form on that patch, break open into painful shallow sores, then scab over and heal within two to six weeks.
The key word with herpes is “painful.” The blisters are filled with clear or straw-colored fluid and tend to cluster together. First outbreaks are usually the worst, sometimes accompanied by fever, fatigue, and swollen lymph nodes. Later outbreaks tend to be milder, shorter, and may involve just one or two sores. Symptoms typically appear about four days after exposure, though the range is two to twelve days.
Syphilis
Syphilis looks completely different from herpes, and the biggest surprise for most people is that it doesn’t hurt. The first sign is a single, firm, painless sore called a chancre, most often appearing on the head of the penis. It’s round, has clean edges, and can easily be mistaken for a harmless bump because it causes no pain or itching. It shows up about three weeks after exposure on average, though the window ranges from 10 to 90 days.
If that sore goes untreated (and it will heal on its own within a few weeks, which tricks people into thinking they’re fine), syphilis progresses to a second stage. About 90% of people with secondary syphilis develop a flat, reddish rash that can appear on the torso, arms, and legs. One distinguishing feature: it often shows up on the palms of the hands and soles of the feet, which most other rashes don’t do. The lesions can be subtle enough to overlook entirely. Secondary syphilis can also cause patchy hair loss, sore throat, and general fatigue.
Genital Warts (HPV)
HPV warts appear as small bumps or groups of bumps on the penis, scrotum, groin, or around the anus. They can be flat or raised, flesh-colored or pink, and sometimes take on a rough, cauliflower-like texture when they cluster together. They’re usually painless and tend to grow slowly over weeks or months.
Warts can take a long time to appear after exposure, anywhere from three weeks to many months, which makes it hard to trace when infection happened. Some warts stay small and barely noticeable, while others grow into larger clusters. The color varies: flesh-toned, pink, reddish-brown, or darker depending on skin tone.
Chlamydia and Gonorrhea
These two bacterial infections don’t typically produce visible sores or bumps. Instead, the most common visible sign is discharge from the penis. Gonorrhea tends to produce a thick, yellowish or greenish discharge, while chlamydia discharge is usually thinner and more watery or cloudy. Both can cause redness or swelling at the opening of the urethra, and burning during urination.
Gonorrhea symptoms usually appear within two to eight days. Chlamydia takes one to three weeks on average. The catch is that many men with chlamydia have no noticeable symptoms at all, which is why it spreads so effectively. Gonorrhea is somewhat more likely to cause obvious symptoms, but asymptomatic cases happen with both.
Molluscum Contagiosum
Molluscum produces small, firm, dome-shaped bumps that are white, pink, or skin-colored. They range from the size of a pinhead to about the size of a pencil eraser. The telltale feature is a small dip or dimple in the center of each bump. They can appear on the penis, inner thighs, lower abdomen, or groin and are generally painless. Symptoms take anywhere from two weeks to six months to show up after contact.
How to Tell STIs Apart From Harmless Conditions
Not every bump on the genitals is an STI. Two common look-alikes cause unnecessary panic.
Pearly penile papules are tiny, smooth, dome-shaped bumps that line the ridge around the head of the penis. They’re typically 1 to 4 millimeters, uniform in size, and arranged in neat symmetrical rows. They’re completely harmless and not sexually transmitted. HPV warts, by contrast, vary in size and shape, can appear anywhere on the genitals, often cluster irregularly, and may develop a rough or cauliflower-like surface over time.
Ingrown hairs can look like herpes at first glance, especially after shaving. An ingrown hair tends to be a single reddish bump that’s warm to the touch, looks like a pimple, and often has a visible hair trapped at the center. Herpes sores look more like open scratches or shallow ulcers, tend to appear in clusters, and often come with systemic symptoms like fever and fatigue that an ingrown hair wouldn’t cause.
When Symptoms Don’t Show Up at All
Several STIs produce no visible signs in men for extended periods. HIV can cause mild flu-like symptoms (body aches, fever) within one to two weeks of infection, then go silent for months to years. Hepatitis B may not cause noticeable symptoms for six weeks to six months. Chlamydia and trichomoniasis are frequently asymptomatic.
This is why visual self-checks alone aren’t reliable. A man can carry and transmit infections without ever seeing a sore, bump, or discharge. Regular testing is the only way to catch infections that don’t announce themselves visually, particularly if you have new or multiple partners.