Sexually transmitted infections look different depending on the type, and many don’t look like anything at all. The majority of new STI cases produce no visible symptoms, which is why testing matters more than visual inspection. But when symptoms do appear, they tend to fall into recognizable patterns: sores, blisters, rashes, warts, unusual discharge, or tiny parasites. Here’s what each one actually looks like.
Genital Herpes
Herpes (HSV) is one of the most recognizable STIs when it’s active. Symptoms tend to appear within about 12 days of exposure, though some people carry the virus for months or years before their first outbreak. The progression follows a predictable pattern.
It starts with a tingling, burning, or shooting pain in the area where the outbreak is about to happen, often in the legs, hips, or buttocks. Within hours or days, small blisters appear around the genitals, anus, or mouth. Those blisters rupture into painful, shallow ulcers that ooze or bleed, then gradually crust over with scabs as they heal. A full outbreak can last two to three weeks the first time and tends to be shorter in later recurrences. Some people also get a fever, fatigue, and swollen lymph nodes during their first episode.
One common source of confusion: herpes blisters can look a lot like ingrown hairs early on, since both start with redness, itching, and raised bumps. The difference is that an ingrown hair usually has a visible hair at the center and looks like a single pimple. Herpes lesions tend to cluster together, may look more like open scratches or raw patches, and often come with flu-like symptoms that an ingrown hair wouldn’t cause.
Genital Warts (HPV)
Human papillomavirus causes genital warts, though most HPV infections never produce visible warts at all. When warts do appear, they show up as small, skin-colored swellings in the genital area. They can also be a slightly different color than the surrounding skin. The texture is the giveaway: when several warts grow close together, they form a bumpy, cauliflower-like cluster. Some genital warts are so small and flat they’re nearly invisible, which is why they can go unnoticed for a long time. There’s no reliable way to predict when warts will appear after infection, since HPV can remain dormant for weeks, months, or even years.
Syphilis
Syphilis changes its appearance dramatically as it progresses through stages, which is part of what makes it tricky to recognize.
In the primary stage, a single small sore called a chancre appears at the spot where the bacteria entered the body. This could be on the genitals, anus, or mouth. The chancre is often painless, firm, and round. Because it doesn’t hurt, many people miss it entirely, and it heals on its own within a few weeks even without treatment. That healing doesn’t mean the infection is gone.
In the secondary stage, a rash develops that typically starts on the trunk (chest, stomach, pelvis, back) and then spreads to the limbs. One of syphilis’s signature traits is a rash on the palms of the hands and soles of the feet, which is unusual for most skin conditions. The rash looks rough, red, or reddish-brown, and it’s often not itchy. It can be so faint that it’s easy to overlook.
Chlamydia and Gonorrhea
These two bacterial infections are grouped together because they often look similar when they do cause symptoms, and more importantly, both frequently cause no visible signs at all. The majority of chlamydia and gonorrhea infections are asymptomatic, meaning you can have one (or both) without ever seeing or feeling anything wrong.
When symptoms do show up, the most noticeable sign is abnormal discharge. This can appear as a yellow discharge from the vagina or urethra, or any discharge that looks, smells, or feels different from what’s normal for you. In people with penises, discharge is often more obvious and may be accompanied by burning during urination. In people with vaginas, the changes can be subtle enough to dismiss as normal variation. Neither infection typically causes the dramatic sores or rashes that herpes or syphilis do, which is exactly why they’re so often missed without a lab test.
Molluscum Contagiosum
Molluscum contagiosum is a viral skin infection that spreads through skin-to-skin contact, including sexual contact. It produces raised, round, skin-colored bumps with one very distinctive feature: a small dent or dimple right at the top center of each bump. This central indentation is the hallmark that sets molluscum apart from other bumps. The bumps are usually painless and firm, and they can appear in clusters in the genital area, inner thighs, or lower abdomen. They’re sometimes mistaken for warts or pimples, but the dimpled center is the clue.
Pubic Lice
Pubic lice, commonly called crabs, are tiny parasites that live in coarse body hair, primarily in the pubic region. Adult lice are about the size of a pencil tip (1.1 to 1.8 mm) and are short, flat, and broader than head lice, giving them a crab-like appearance. They’re technically visible to the naked eye, but a magnifying glass helps. What you’re more likely to notice first is intense itching and small blue-gray spots on the skin where the lice have been feeding. You may also see tiny oval nits (eggs) attached to the base of hair shafts.
Why Many STIs Look Like Nothing
More than 1 million curable STIs are acquired every day worldwide among people aged 15 to 49, and the majority of those infections are asymptomatic. That statistic is worth sitting with. Chlamydia, gonorrhea, HPV, and even herpes can all be present in your body without producing any visible sign. Syphilis can appear briefly, heal itself, and then go silent for years while still being transmissible and still doing internal damage.
This is the most important thing to understand about what STIs look like: many of them look like absolutely nothing. Visual self-checks are useful for catching the infections that do produce symptoms, but they’re not a substitute for testing. If you’re sexually active with new or multiple partners, regular screening catches what your eyes can’t.
What to Look For Overall
- Blisters or open sores around the genitals, anus, or mouth, especially in clusters: think herpes or syphilis.
- A single painless sore that’s firm and round: think primary syphilis.
- Bumpy, cauliflower-textured growths that are skin-colored: think genital warts from HPV.
- Smooth, dome-shaped bumps with a dimpled center: think molluscum contagiosum.
- Unusual discharge that’s yellow or different from your baseline: think chlamydia or gonorrhea.
- A rash on the palms or soles that’s rough and reddish-brown: think secondary syphilis.
- Intense itching with tiny visible insects in pubic hair: think pubic lice.
Any new bump, sore, rash, or discharge in the genital area is worth getting checked, even if it doesn’t match these descriptions perfectly. STIs don’t always present textbook cases, and the ones that cause the least visible damage on the outside can still cause serious complications if left untreated.