Several STIs can make you itch down there — genital herpes, trichomoniasis, pubic lice (crabs), and scabies are the usual culprits. But itching is just as often something else entirely: a yeast infection, eczema, contact dermatitis, or plain dry skin. Because these overlap so heavily, only a test tells you which one it is.
Herpes simplex virus
Trichomonas vaginalis
Pthirus pubis
Human itch mite
| Item | Value |
|---|---|
| Genital herpes | managed — Herpes simplex virus |
| Trichomoniasis | curable — Trichomonas vaginalis |
| Pubic lice (crabs) | curable — Pthirus pubis |
| Scabies | curable — Human itch mite |
The short list: what's likely causing genital itching
Genital itching has a manageable list of suspects. On the STI side, four conditions account for most cases that turn out to be sexually transmitted: herpes, trichomoniasis, pubic lice, and scabies. Off the STI side, yeast infections, skin conditions like eczema and contact dermatitis, and simple dryness are extremely common, and often more likely than an infection. None of these reliably announces itself by feel alone.
Which STIs cause genital itching
Genital herpes
Genital herpes is caused by two viruses, herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) CDC. The majority of infections cause no symptoms or very mild ones, and most people who carry HSV-2 don't know it. When herpes does flare, the pattern is small blisters that break open into painful sores on or around the genitals, rectum, or mouth, often with a tingling or itchy 'prodrome' beforehand. A first outbreak can come with flu-like symptoms like fever, body aches, and swollen glands, and the sores can take a week or more to heal. Repeat outbreaks tend to be shorter and milder.
So if your itch is paired with painful blisters or sores, herpes moves up the list. If it's pure itch with no lesions, herpes is a less typical fit. Antivirals are the mainstay of management; some people also ask about complementary options, which we cover in alternative herpes treatments.
Trichomoniasis
Trichomoniasis is caused by a microscopic parasite, Trichomonas vaginalis, and it's the most common curable STI CDC. About 70% of infected people have no symptoms at all, which is why it spreads quietly. When symptoms do show, women may notice itching, burning, redness or soreness of the genitals, discomfort urinating, and a clear, white, yellowish, or greenish discharge with a fishy smell. Men sometimes get itching or irritation inside the penis and burning after urinating or ejaculating, but men are commonly silent carriers.
Itching plus a frothy or fishy-smelling discharge is a classic trich pattern. Symptoms, when they appear, can show up 5 to 28 days after infection, sometimes much later. We break down the full picture in our guide to trichomoniasis symptoms.
Pubic lice (crabs)
Pubic lice — 'crabs' — are tiny blood-feeding insects (Pthirus pubis) that live mainly in coarse pubic and perianal hair, and occasionally the armpits, chest, beard, or eyelashes CDC. They spread mostly through sexual contact. Most infestations cause no symptoms, but when they do, you get itching in the genital area along with live lice or nits (eggs) cemented to the hair shafts that you can often see. Scratching can lead to sores or secondary skin infection.
If you spot specks moving in the hair or tiny eggs glued near the base of a shaft, that points to lice rather than the other suspects. Treatment is straightforward, and stopping a repeat infestation matters just as much; see how to prevent crabs & avoid reinfestation.
Scabies
Scabies is caused by the human itch mite, Sarcoptes scabiei, which burrows into the upper layer of skin to live and lay eggs CDC. In adults it's frequently passed through sexual or skin-to-skin contact. It causes intense itching that's worse at night, plus a pimple-like rash and thread-thin, crooked 'burrows' where the mite has tunneled. Common sites include between the fingers, the wrists, the waist, the buttocks, and the penis. After a first infestation, symptoms typically take 4 to 8 weeks to develop, and a person can spread it before any itch begins.
Night-worse itching that also shows up on the hands, wrists, or waist rather than just the genitals leans toward scabies over a strictly genital STI.
When genital itching is NOT an STI
Plenty of genital itching has nothing to do with sex. The common non-STI causes are yeast infections (an overgrowth of normal skin yeast, often with thick discharge and itch), eczema and contact dermatitis (irritated, inflamed skin from soaps, detergents, fragrances, latex, or new products), and simple dry skin. These can itch every bit as much as an STI, and they're frequently the real answer, especially when there's no new partner and no other STI symptoms.
How to tell them apart
Look past the itch and notice what travels with it. Painful blisters or sores point toward herpes. A fishy, frothy discharge points toward trich. Visible bugs or eggs in the hair point toward crabs. Night-worse itch on the hands, wrists, and waist points toward scabies. Thick, cottage-cheese discharge or itch after a new soap or product points away from an STI and toward yeast or irritation.
These patterns overlap badly, and several of these infections are frequently silent, so you can't reliably sort them by sight or sensation. A test settles which one, if any, it is.
Side-by-side: genital itch by cause
| Cause | Itch pattern | What travels with it | STI? |
|---|---|---|---|
| Genital herpes | Itch/tingle, then pain | Blisters breaking into sores; possible flu-like signs | Yes (HSV-1/HSV-2) |
| Trichomoniasis | Itch, burning, soreness | Frothy, fishy discharge; burning on urination | Yes (parasite) |
| Pubic lice (crabs) | Genital-area itch | Visible lice or nits in pubic hair | Yes (insect) |
| Scabies | Intense, worse at night | Burrows and rash on hands, wrists, waist, genitals | Often, in adults (mite) |
| Yeast / eczema / irritation | Itch, can be intense | Thick discharge, redness, or recent new product | No |
How it's tested
Testing depends on what's suspected: a swab of a sore for herpes, a urine sample or vaginal swab for trichomoniasis, and a quick visual exam for lice or scabies, sometimes with a magnifying lens or a skin scraping. For trich, NAAT is the preferred test and is highly accurate CDC, 2021; herpes is confirmed by type-specific testing of an active lesion CDC. If you're unsure where to start, get tested and let the clinician pick the right panel.
What to do next
All four of these STIs are treatable, and the non-STI causes usually clear with the right cream or a change in products. Because the symptoms overlap, you can't safely self-diagnose this; a test turns a guess into an answer. Testing is often free or low-cost at health departments, Planned Parenthood, and Title X clinics, and results usually come back within a few days. If you were recently exposed, timing matters — see when to test after exposure so you don't test too early.
Red flags — when to get seen urgently
- Painful blisters or open sores on the genitals, rectum, or mouth, especially with fever or swollen glands.
- Spreading redness, warmth, pus, or worsening pain — signs the skin may be infected from scratching.
- Severe pain with urination or an inability to urinate.
- Itching that keeps you up at night and rash spreading to the hands, wrists, or waist.
- Any new genital symptom after a recent new partner, or symptoms that don't improve with over-the-counter care.