Most STIs either cause visible changes you can spot on your skin and genitals, or they cause no visible signs at all. What you see depends entirely on which infection is involved. Some produce sores, others cause bumps or rashes, and several change the color or texture of discharge. The tricky part: the majority of STIs are asymptomatic, meaning you can have one and see nothing unusual.
Here’s what each common STI actually looks like when it does show up.
Sores and Ulcers: Syphilis and Herpes
Syphilis and herpes both cause open sores on the genitals, mouth, or surrounding skin, but the sores look quite different from each other.
Syphilis
The first sign of syphilis is a single, smooth, hard sore called a chancre. It develops on the genitals, lips, mouth, or tongue, typically about 21 days after exposure (though the window ranges from 10 to 90 days). The sore may resemble a pimple and can be so small you don’t notice it. It’s painless, which is one reason people miss it entirely.
If syphilis goes untreated, it moves into a second stage weeks later. This produces a rough, red or brown rash that can appear on your back, chest, palms of your hands, or bottoms of your feet. A rash on the palms or soles is unusual for most skin conditions, so it’s a distinctive signal. You may also develop sores inside your mouth, vagina, or anus during this stage.
Herpes
Herpes creates clusters of small, fluid-filled blisters that eventually break open, form shallow ulcers, then crust over and heal. On the genitals, blisters appear on and around the vulva, penis, or anus. On the mouth, they show up on or around the lips (commonly called cold sores). Blisters typically appear about four days after exposure, though the range is 2 to 12 days.
Before blisters become visible, the skin often tingles, itches, or burns for up to 48 hours. A first genital outbreak may also come with fever, headache, and swollen lymph nodes. Later outbreaks tend to be milder and shorter.
Bumps and Growths: HPV and Molluscum
Genital Warts (HPV)
Genital warts from HPV look like small, skin-colored bumps on or around the genitals and anus. They can also appear slightly darker or lighter than the surrounding skin. When several warts cluster together, they take on a cauliflower-like texture. In many cases, warts are so small and flat that you can’t see them with the naked eye. They may take anywhere from three weeks to many months to appear after exposure, which makes it hard to trace when you were infected.
In people with weakened immune systems, warts can occasionally multiply into larger clusters. But for most people, they stay small and may resolve on their own over time.
Molluscum Contagiosum
Molluscum produces small, pearly, dome-shaped bumps averaging 2 to 5 millimeters across. The signature feature is a tiny dimple or depression in the center of each bump. If you squeeze one (not recommended, as this spreads the virus), it releases a white, cheesy material. The bumps are painless and can appear anywhere on the genitals, thighs, or lower abdomen. They’re sometimes mistaken for pimples, but the central dimple and pearly sheen set them apart.
Changes in Discharge: Chlamydia and Gonorrhea
Chlamydia and gonorrhea don’t typically cause visible skin changes. Instead, they affect discharge. Both can produce cloudy, yellow, or green discharge from the vagina or penis. In men, discharge from the tip of the penis (especially in the morning) is a common early signal of gonorrhea. Women may notice a change in the color, amount, or smell of vaginal discharge, though the shift can be subtle enough to dismiss.
Both infections can also cause burning during urination, which isn’t something you can see but is often the symptom that prompts people to get tested. The bigger issue with chlamydia and gonorrhea is that many people experience no symptoms at all, allowing the infections to spread silently and potentially cause complications like pelvic inflammatory disease or fertility problems.
Rashes That Signal Broader Infection: HIV
About half of people with a new HIV infection develop a rash during the initial stage, typically appearing three days after a fever starts and lasting five to eight days. The rash consists of small (5 to 10 mm), well-defined, flat or slightly raised reddish spots, concentrated mainly on the front of the chest. It can look like many other viral rashes, which is why it’s rarely recognized as HIV-related without testing.
This early rash is part of a flu-like illness that occurs two to four weeks after exposure. It resolves on its own, but the virus remains. HIV has no lasting visible signs in its early years, making it impossible to identify by appearance alone.
What Looks Like an STI but Isn’t
Not every bump or irritation in the genital area is an STI. Ingrown hairs from shaving are extremely common and can look similar to herpes blisters. Both appear as red, irritated bumps, sometimes with fluid inside. A few differences help distinguish them: ingrown hairs tend to appear within a day or two of shaving, center around a visible trapped hair, and occur as isolated bumps rather than clusters. Herpes blisters appear about four days after sexual exposure, cluster together, and are preceded by tingling or burning in the skin.
Fordyce spots are another common source of worry. These are tiny, pale or yellowish bumps on the shaft of the penis or the labia that are simply visible oil glands. They’re completely normal, painless, and don’t change over time. Skin tags, cysts, and friction irritation can also mimic the look of STIs.
Most STIs Are Invisible
The most important thing to understand about STI appearance is that most infections produce no visible signs. The World Health Organization notes that the majority of STIs are asymptomatic. Chlamydia, gonorrhea, HPV, herpes, and HIV can all be present in your body without causing anything you’d notice in a mirror. This is why visual self-checks, while useful, are not a substitute for testing. Many people transmit infections without ever knowing they carry one.
If you’ve noticed something unusual on your skin or genitals, the descriptions above can help you understand what you might be dealing with. But a sore that looks like syphilis could be herpes, a bump that looks like a wart could be molluscum, and something that looks alarming could be a harmless ingrown hair. Testing is the only way to know for certain what you’re looking at.