The most common sexually transmitted infections range from those that cause obvious sores and rashes to those with no visible signs at all. Understanding what each one looks like can help you recognize symptoms early, but it’s worth knowing upfront that many STIs produce no visible symptoms whatsoever. Roughly 50 to 60% of chlamydia, gonorrhea, and trichomoniasis cases in women show no signs at all. With that caveat, here’s what each of the most common STIs can look like when symptoms do appear.
1. Genital Herpes (HSV-1 and HSV-2)
Herpes is one of the most visually recognizable STIs. It starts with small bumps or blisters that appear in clusters around the genitals, anus, or mouth. These blisters are fluid-filled, and within a few days they rupture into open, shallow ulcers that may ooze or bleed. Over the following week or so, they crust over with scabs and gradually heal.
Before an outbreak appears, many people experience warning signs: tingling, itching, or shooting pain in the legs, hips, or buttocks. Outbreaks tend to recur, though they usually become less severe over time. Between outbreaks, herpes produces no visible signs, which is one reason it spreads so easily.
2. Syphilis
Syphilis changes appearance dramatically as it progresses through stages. In the primary stage, it produces a single firm, round, painless sore called a chancre. This sore can appear on the genitals, inside the vagina, on the surface of the tongue, or around the anus. Because it’s painless, it often goes unnoticed.
If untreated, syphilis enters its secondary stage, producing a widespread rash that can cover the back, chest, and extremities. One telltale feature: the rash often appears on the palms of the hands and soles of the feet, which is unusual for most skin conditions. These lesions are typically flat or slightly raised and reddish-brown. Syphilis remains a serious concern, with over 190,000 total cases reported in the U.S. in 2024.
3. Genital Warts (HPV)
Genital warts caused by certain strains of human papillomavirus appear as small, skin-colored swellings in the genital area. They can be flat or slightly raised, and when several cluster together they take on a distinctive cauliflower-like texture. The bumps may match your skin tone or appear slightly different in color. They’re typically painless but can itch.
Most HPV infections don’t cause warts at all. The strains that cause warts are different from the high-risk strains linked to cervical and other cancers, which produce no visible symptoms and are only detected through screening.
4. Chlamydia
Chlamydia is the most commonly reported STI in the United States, with over 1.5 million cases in 2024, yet it rarely produces visible signs you’d notice by looking. When it does cause symptoms, the most common visual indicator is an abnormal discharge: yellowish from the vagina or urethra. Women may also notice bleeding between periods. Men may see a clear or cloudy discharge from the penis.
The majority of chlamydia infections are completely silent. About 61% of cases in women produce no symptoms, which is why routine annual screening is recommended for all sexually active women under 25.
5. Gonorrhea
Gonorrhea’s visual signs overlap significantly with chlamydia. In women, it can cause a yellow or greenish vaginal discharge. In men, it more often produces noticeable symptoms: a thick, yellowish or greenish discharge from the penis, sometimes described as pus-like, along with pain during urination.
Over half of gonorrhea infections in women are asymptomatic. The U.S. reported about 543,000 gonorrhea cases in 2024. Left untreated, it can cause internal damage without ever producing obvious external signs.
6. Trichomoniasis
Trichomoniasis is caused by a parasite rather than a bacterium or virus. When symptoms appear in women, the hallmark sign is a frothy vaginal discharge that can range from clear to white, yellowish, or greenish, often with a noticeable fishy smell. The genital area may appear red and irritated. During a clinical exam, the cervix sometimes shows tiny red spots, giving it a speckled appearance.
Men with trichomoniasis rarely show visible signs, which makes them effective carriers. About 57% of infections in women produce no symptoms.
7. HIV
HIV doesn’t produce genital sores or discharge. Its earliest visual sign, when one appears at all, is a seroconversion rash that develops two to four weeks after infection. This rash is typically flat or slightly raised, reddish, and widespread across the torso. It looks more like a general viral illness than a sexually transmitted infection and is easily mistaken for a reaction to medication or a mild flu-related rash. Fever, sore throat, and swollen lymph nodes often accompany it.
Because these early symptoms are so nonspecific and short-lived, HIV is rarely identified by appearance alone. Testing is the only reliable way to detect it.
8. Hepatitis B
Hepatitis B primarily affects the liver, but it can produce visible signs. About 10 to 20% of people with acute hepatitis B infection develop a serum sickness-like reaction before jaundice sets in. This can include a skin rash that ranges from flat red patches to raised hive-like welts or small nodular lesions, usually accompanied by fever and joint pain.
The more recognizable visual sign comes later: jaundice, a yellowing of the skin and the whites of the eyes caused by the liver’s inability to process bilirubin properly. Dark urine and pale stools often accompany it.
9. Molluscum Contagiosum
Molluscum contagiosum produces one of the most distinctive-looking skin findings of any STI. The bumps are small, firm, dome-shaped, and usually white, pink, or skin-colored. They range from the size of a pinhead to a pencil eraser. The key identifying feature is a small dimple or dip in the center of each bump, which distinguishes them from most other skin growths.
In adults, when molluscum is sexually transmitted, the bumps appear around the genitals, inner thighs, and lower abdomen. They’re painless and can persist for months before the immune system clears them.
10. Pubic Lice and Scabies
Pubic lice (often called crabs) are tiny parasites about the size of a pencil dot, greyish-brown, and difficult to spot with the naked eye. What you’re more likely to notice are the eggs: small white or tan nits attached to the base of pubic hair. Intense itching is the primary symptom, and you may see small bluish spots on the skin from bites.
Scabies mites are even smaller, invisible without magnification. They burrow under the skin to lay eggs, leaving thin, irregular tracks that look like tiny raised lines. These burrows appear most often between fingers, on wrists, and around the waistline or genitals. The itching from scabies is often severe and worst at night.
How STIs Differ From Common Skin Irritation
Many people searching for STI images are actually trying to figure out whether a bump or rash in the genital area is something to worry about. Razor burn causes a blotchy red rash across the shaved area, while razor bumps (ingrown hairs) look like small individual pimples scattered across the skin. Neither forms the fluid-filled clusters characteristic of herpes, and neither produces the firm, painless, solitary sore of primary syphilis.
A few distinguishing clues: herpes blisters develop in tight clusters and often recur in the same spot. Syphilis chancres are painless and solitary. Genital warts are firm and irregular in texture. Razor bumps, by contrast, tend to appear in areas you’ve recently shaved, look like typical pimples, and resolve within a week or two without recurring. If you notice fluid-filled blisters, painless ulcers, or any growth that doesn’t resolve on its own, testing is the only way to distinguish an STI from a benign skin condition.
Why Visual Identification Isn’t Enough
The biggest challenge with identifying STIs by appearance is that the most common ones, chlamydia and gonorrhea, often look like nothing at all. And infections that do cause visible signs, like herpes and syphilis, can appear in internal locations you can’t easily see. Screening guidelines recommend annual testing for chlamydia and gonorrhea in sexually active women under 25, syphilis screening for all pregnant people and anyone with risk factors, and HIV testing at least once for all adults. Visual checks are a useful starting point, but they catch only a fraction of active infections.