Genital itching can be a sign of several sexually transmitted infections, most commonly genital herpes, trichomoniasis, pubic lice (crabs), and scabies. But it's just as often caused by non-STI problems like yeast infections, eczema, or contact dermatitis. Because these overlap so much, a test is what tells you which one you have.
painful blisters that crust over; tends to recur
frothy, itchy discharge with an odor
itching with visible lice or nits in coarse hair
intense night-time itch with thread-like burrows
| Item | Value |
|---|---|
| Genital herpes | managed — painful blisters that crust over; tends to recur |
| Trichomoniasis | curable — frothy, itchy discharge with an odor |
| Pubic lice (crabs) | curable — itching with visible lice or nits in coarse hair |
| Scabies | curable — intense night-time itch with thread-like burrows |
Which STIs actually cause genital itching?
Four STIs are the usual suspects when itching is the main complaint. Each has a tell-tale pattern, but none of them itches in a way unique enough to diagnose by feel alone. Here's what each one is and what it tends to look like.
Genital herpes
Genital herpes is caused by two viruses, herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) CDC, About Genital Herpes. Most people have no symptoms or very mild ones, and the majority of HSV-2 infections are never diagnosed, so plenty of people carry it without knowing.
When symptoms do show, the classic first outbreak is a cluster of blisters that break open into painful sores, often on or around the genitals, rectum, or mouth, taking a week or more to heal. Itching or tingling can come first as a warning sign, sometimes alongside flu-like symptoms like fever, body aches, and swollen glands. Repeat outbreaks are shorter and milder, and many are preceded by that same itchy or tingling prodrome before any sore appears. If herpes is your diagnosis, it's worth reading up on suppressive options and alternative herpes treatments.
Trichomoniasis (trich)
Trichomoniasis is caused by a tiny protozoan parasite, Trichomonas vaginalis, and it's the most common curable STI CDC, About Trichomoniasis. About 70% of infected people have no signs or symptoms at all, so it spreads quietly.
When symptoms appear, women often notice itching, burning, redness or soreness of the genitals, discomfort with urination, and a discharge that can be clear, white, yellowish, or greenish, sometimes with a fishy smell. Men, who are commonly asymptomatic, may feel itching or irritation inside the penis, burning after peeing or ejaculating, or have some discharge. Symptoms, when they come, may show up roughly 5 to 28 days after infection, but they can also appear much later. If trich is on the table, here's trichomoniasis testing & diagnosis in detail.
Pubic lice (crabs)
Pubic lice — "crabs" — are Pthirus pubis, small blood-feeding insects that live mainly in coarse pubic and perianal hair, and occasionally the armpits, chest, beard, or even eyelashes CDC, About Pubic Lice. They spread mostly through sexual contact. Most infestations cause no symptoms, but when they do, you get itching in the genital area plus visible lice or nits (their eggs) glued to the hair shafts. Scratching can lead to sores or skin infection. Unlike herpes or trich, you can often actually see the cause. More on crabs symptoms if you think this is it.
Scabies
Scabies is caused by the human itch mite, Sarcoptes scabiei, which burrows into the top layer of skin to live and lay eggs CDC, About Scabies. In adults it's frequently passed through sex. The hallmark is intense itching, classically worse at night, with a pimple-like itchy rash and tiny raised, crooked lines (burrows). Common spots include between the fingers, the wrists, and the penis, waist, and buttocks.
Something that catches people off guard: after a first infestation, symptoms typically take 4 to 8 weeks to develop CDC, Scabies signs & symptoms, and you can pass it to a partner before you ever start itching. Because mites can be reintroduced, treating partners and bedding matters; see scabies reinfection for prevention.
When the itch is NOT an STI
Not every itch downstairs is an STI, far from it. Genital itching also comes from yeast infections, eczema, contact dermatitis (a reaction to soaps, detergents, condoms, or lubricants), and plain dry skin. These are extremely common and have nothing to do with sex.
A yeast infection often brings a thick, white discharge and itching; eczema and contact dermatitis tend to cause red, scaly, or irritated patches that flare after contact with a new product. These look and feel a lot like the STIs above, and several causes are frequently silent or vague, so sight alone can't sort them out.
How do you tell them apart?
There are discriminating clues, even if none is foolproof. Visible bugs or eggs in the hair point to crabs. Burrows and night-worsening itch suggest scabies. Painful blisters and sores suggest herpes. Itching with an abnormal, sometimes fishy-smelling discharge leans toward trich or a yeast infection. A flare right after a new soap or condom hints at contact dermatitis.
These conditions overlap too much to tell apart by sight, and several are often silent. A test settles which one it is, if any. Self-diagnosing this is a losing game.
Genital itching: STI vs. non-STI at a glance
| Cause | STI? | Tell-tale signs | How it's confirmed |
|---|---|---|---|
| Genital herpes | Yes | Tingling/itch, then painful blisters and sores; possible flu-like feeling | Swab of a sore (NAAT or culture) |
| Trichomoniasis | Yes | Itch/burning, abnormal often fishy discharge; frequently no symptoms | NAAT on swab or urine |
| Pubic lice (crabs) | Yes | Itch plus visible lice or nits on pubic hair | Finding lice/nits by eye or lens |
| Scabies | Often | Intense night itch, burrows, rash between fingers/genitals | Clinical exam; skin-scraping if needed |
| Yeast infection | No | Itch with thick white discharge | Exam/swab |
| Eczema / contact dermatitis | No | Red, scaly, irritated skin; flares after new products | Clinical exam |
How is it tested?
Testing depends on what's suspected. A herpes sore gets confirmed by swabbing it for type-specific virologic testing (NAAT or culture), which works best while lesions are present CDC, Herpes Testing. Trich is best found with a NAAT, a highly accurate test run on a vaginal swab or urine sample CDC, Trichomoniasis Tx Guidelines, 2021. Lice and scabies are usually diagnosed by simply looking — spotting lice or nits, or the burrows and rash, sometimes with a skin scraping for scabies CDC DPDx, Pthiriasis.
In practice that means a urine sample, a self-collected swab, or a quick exam, depending on the suspect. It's free or low-cost at health departments, Planned Parenthood, and Title X clinics, with results usually back in a few days. When you're ready to get tested, that turns a guess into an answer. If you're counting days since a hookup, check when to test after exposure so you don't test too early.
What to do next
All four of these STIs are treatable, and the non-STI causes are too. Trich and the bug infestations (lice and scabies) are curable; herpes isn't cured but is well controlled with medication. Don't start guessing at creams or borrowing a partner's pills — get the right diagnosis first, then match the treatment to it. Treating partners at the same time prevents the ping-pong reinfection that's especially common with trich, lice, and scabies.
Red flags — when to be seen urgently
- You have severe pain, spreading redness, pus, or fever with the rash or sores — signs of a skin infection that needs prompt care.
- You can't urinate or it's extremely painful, which can happen during a first herpes outbreak.
- Sores are widespread or worsening rather than healing after a week or more.
- You're pregnant and develop new genital sores, discharge, or a rash.
- The itch and rash are getting dramatically worse despite over-the-counter treatment, suggesting the wrong diagnosis.