Several STIs can cause genital bumps or lumps — most commonly HPV (genital warts), molluscum contagiosum, and genital herpes. But plenty of harmless, non-STI conditions look almost identical: Fordyce spots, pearly penile papules, skin tags, cysts, and ingrown hairs. Because these overlap so much by sight, a test, not the bump itself, is what tells you which one it is.
painless warts; flesh-colored, cauliflower-like
pearly, dome-shaped bumps with a central dimple
painful blisters that crust over; tends to recur
| Item | Value |
|---|---|
| HPV & genital warts | managed — painless warts; flesh-colored, cauliflower-like |
| Molluscum contagiosum | curable — pearly, dome-shaped bumps with a central dimple |
| Genital herpes | managed — painful blisters that crust over; tends to recur |
Which STIs cause genital bumps or lumps?
Three infections account for most STI-related bumps, and each has a recognizable pattern. The catch is that the patterns blur in real life — and all three can be present without any visible bump at all. Use the descriptions below to narrow your suspicion, not to close the case.
HPV and genital warts
HPV is the most common STI CDC HPV. Genital warts usually show up as a small bump or a cluster of bumps in the genital area — they can be flat, raised, or shaped like a tiny cauliflower, and they're typically soft and painless. Some people get one; others get several grouped together.
Timing is unpredictable. Warts can appear months or years after you acquired HPV, and there's no way to pin down exactly when you got it CDC Pink Book. The strains that cause warts are different from the high-risk strains tied to cancer — and high-risk HPV is typically silent, causing no bump and no symptoms at all. There's no routine HPV test for men, adolescents, or women under a certain age, so a wart you can see is often the only sign the virus is around CDC STI Tx. Learn more about hpv & genital warts.
Molluscum contagiosum
Molluscum is a benign, usually mild skin infection caused by a poxvirus, and in adults it often spreads through sexual contact CDC Molluscum. Its signature is a small, firm, pearly bump — white, pink, or skin-colored, often with a tiny dimple or dip in the center. The bumps run from pinhead to pencil-eraser size and can appear almost anywhere on the body except, rarely, the palms or soles. They may be itchy or a little sore CDC Molluscum clinical.
That central dimple is the most useful clue distinguishing molluscum from warts, which usually lack it. Read more on molluscum contagiosum bumps.
Genital herpes
Genital herpes is caused by two viruses, HSV-1 and HSV-2 CDC Herpes. When it does produce a lesion, the pattern is distinct: a first outbreak begins as blisters that break open into painful, often raw sores, which can take a week or more to heal. Flu-like symptoms — fever, body aches, swollen glands — sometimes come with that first episode. Sores can appear on or around the genitals, rectum, or mouth. Repeat outbreaks are shorter and milder, and some people feel a tingling or burning prodrome in the area a day or so before a sore shows up.
Crucially, most people with herpes have no or very mild symptoms and don't know they're infected — the majority of HSV-2 infections are never diagnosed. So a smooth, painless bump is far more likely warts or molluscum than herpes; painful, clustered blisters or open sores point toward herpes. If you're weighing how to manage outbreaks, see alternative herpes treatments.
When it's NOT an STI
A bump downstairs is a normal reason to worry, but most of the time it isn't an infection at all. Common harmless causes include:
- Fordyce spots — small, pale or yellowish enlarged oil glands, often in rows on the shaft or labia; completely normal and not contagious.
- Pearly penile papules — tiny, uniform, dome-shaped bumps lined up around the rim of the glans; a normal anatomical variant, not an infection.
- Skin tags — soft, flesh-colored flaps of skin that can show up in skin folds; harmless.
- Cysts — fluid- or keratin-filled lumps under the skin that feel firm and round; usually benign.
- Ingrown hairs — red, sometimes tender bumps from shaving or waxing, occasionally with a visible hair trapped underneath.
All of these are common and require no treatment. The problem is that they can mimic warts or molluscum closely enough to fool the eye.
How to tell them apart
A few discriminating features help you sort the likely cause, even if they can't confirm it:
- Texture and shape: cauliflower-like or flat bumps suggest warts; firm pearly bumps with a central dimple suggest molluscum; fluid-filled blisters that ulcerate suggest herpes.
- Pain: warts, molluscum, and most non-STI bumps are painless; herpes lesions are typically painful or burning.
- Clustering: herpes blisters tend to come in tight groups; pearly penile papules and Fordyce spots line up in neat, symmetrical rows.
- Course over time: herpes sores crust and heal within roughly a week or two, while warts and molluscum persist and may slowly spread.
- Symmetry and uniformity: normal anatomical bumps look alike and evenly placed; STI bumps are often irregular.
Even with all that, these conditions overlap too much to tell apart by sight alone, and several are frequently silent. A test — not the look of the bump — is what settles which one it is, if any CDC Herpes testing.
Side-by-side comparison
| Cause | Typical look | Pain? | Spreads? |
|---|---|---|---|
| Genital warts (HPV) | Soft bumps, flat or cauliflower-like, single or grouped | Usually painless | Yes (STI) |
| Molluscum contagiosum | Firm pearly bumps, ~2–5 mm, with a central dimple | May itch or be sore | Yes (often sexual in adults) |
| Genital herpes | Blisters that break into painful sores, often clustered | Painful/burning | Yes (STI) |
| Fordyce spots | Small pale/yellow glands, often in rows | No | No |
| Pearly penile papules | Uniform dome bumps around the glans rim | No | No |
| Cysts / skin tags / ingrown hairs | Firm lumps, soft flaps, or red shaving bumps | Usually no (ingrown hairs may be tender) | No |
How it's tested
Testing depends on what's suspected — a quick visual exam can identify classic warts or molluscum, while herpes is confirmed by swabbing an active lesion for type-specific virologic testing (NAAT or culture), which works best on a fresh sore CDC Herpes Tx. In practice you'll give a urine sample, a self-collected swab, or have a brief exam; results usually come back within a few days. You can get tested at health departments, Planned Parenthood, and Title X clinics, often free or low-cost. If you're timing it after a possible exposure, check when to test after exposure.
What to do next
Overlapping symptoms are exactly why you usually can't self-diagnose a genital bump — a test is what turns a guess into an answer. Don't pick, scratch, or shave the area, which can spread molluscum or warts. Get an in-person evaluation if the bump is painful, growing, or you've had a possible exposure, and ask the clinician to confirm the cause before treating it. If it turns out to be herpes or warts, treatment is straightforward, and your clinic can walk you through the options.
Red flags — when to get seen urgently
- Painful blisters or open sores, especially with fever, body aches, or swollen glands — this pattern fits a first herpes outbreak and is worth a prompt swab.
- A bump that bleeds, grows quickly, changes color, or doesn't heal — anything persistent or atypical deserves an exam.
- Bumps with pus, spreading redness, or significant pain, which can signal a secondary infection.
- Trouble urinating, severe genital pain, or sores near the eyes — get care the same day.