Pain during sex (dyspareunia) can be an STI symptom — the usual infectious culprits are pelvic inflammatory disease (PID), genital herpes, and trichomoniasis. But many cases aren't an STI at all: vaginal dryness, vaginismus, and endometriosis cause it too. Because these overlap so much, a test tells you which one it is.
Ascending infection of the upper female genital tract
Herpes simplex virus
Trichomonas vaginalis
| Item | Value |
|---|---|
| Pelvic inflammatory disease (PID) | curable — Ascending infection of the upper female genital tract |
| Genital herpes | managed — Herpes simplex virus |
| Trichomoniasis | curable — Trichomonas vaginalis |
It helps to think about where the pain is. Pain at the entrance (introital or entry dyspareunia) points more toward surface causes like sores, irritation, dryness, or muscle spasm. Deep pelvic pain with thrusting (deep dyspareunia) points more toward something higher up, like inflamed reproductive organs. That split won't diagnose you, but it's a useful starting clue when you talk to a clinician.
Which STIs cause pain during sex?
Pelvic inflammatory disease (PID)
PID is an infection of the upper female reproductive organs — the uterus, fallopian tubes, and ovaries — and it's often a complication of untreated STIs like chlamydia and gonorrhea that have traveled up from the cervix CDC, About PID. That higher location is why PID is the classic cause of deep pain during sex: thrusting jostles inflamed organs.
Beyond painful or bloody sex, PID can bring lower abdominal or pelvic pain, unusual discharge with a bad odor, fever, burning when you urinate, and bleeding between periods. Symptoms are frequently mild or absent, so many people don't realize they have it, and a silent chlamydia infection can quietly become PID and threaten fertility. If a partner has been treated, you may be wondering whether the same applies to you; here's does your partner need treatment for pid?.
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. When it causes pain during sex, it's usually entry pain: an outbreak produces blisters that break into raw, painful sores on or around the genitals, rectum, or mouth, and contact with those sores hurts.
A first outbreak is typically the worst, with sores that take a week or more to heal, sometimes with flu-like symptoms like fever, body aches, and swollen glands. Repeat outbreaks are shorter and milder, and some people get a warning prodrome (tingling or itching) before sores appear. Most people with herpes have no or very mild symptoms and never know they're infected, so the majority of HSV-2 infections go undiagnosed. Painful sex during a visible outbreak is one of the more recognizable presentations. For managing recurrences, see alternative herpes treatments.
Trichomoniasis
Trichomoniasis is caused by the protozoan parasite Trichomonas vaginalis and is the most common curable STI CDC, About Trichomoniasis. When it causes pain with sex, it's the entry/irritation type — the infection inflames the vagina and vulva, producing itching, burning, redness or soreness of the genitals, discomfort urinating, and a clear, white, yellowish, or greenish discharge with a fishy smell.
About 70% of infected people have no signs or symptoms at all. In men it's even quieter: itching inside the penis, burning after urinating or ejaculating, or discharge, but men are commonly asymptomatic. When symptoms do show up, they may appear about 5 to 28 days after infection, though they can surface much later. A fuller rundown of how it presents is in trichomoniasis symptoms.
When it's NOT an STI
Plenty of painful sex has nothing to do with an infection. Three common non-STI causes:
- Vaginal dryness — when there isn't enough lubrication (often from low estrogen around menopause, breastfeeding, certain medications, or insufficient arousal), friction makes penetration burn or sting. This is classic entry pain.
- Vaginismus — an involuntary tightening of the pelvic-floor muscles around the vaginal opening that makes penetration painful or impossible. It's a reflex, not a choice, and often has an anxiety or prior-pain component.
- Endometriosis — when tissue similar to the uterine lining grows outside the uterus. It can tether and inflame pelvic structures, causing deep pain with sex along with painful periods.
How to tell them apart
You can't reliably tell these apart by sight or symptom alone — they overlap too much, and several (PID, herpes, trich) are frequently silent. A test settles which one it is, if any. Still, a few discriminating features help you and your clinician aim:
- Visible sores or blisters that themselves hurt point toward herpes.
- Itching, burning, and a fishy-smelling discharge point toward trichomoniasis (or another vaginitis).
- Deep pain plus fever, abnormal bleeding, or foul discharge raises concern for PID.
- Deep pain that tracks with your period, with no infectious signs, leans toward endometriosis.
- Burning friction with no discharge or sores, especially with low arousal or around menopause, suggests dryness.
- Muscle tightening or 'a wall' at the opening before any pain points to vaginismus.
| Cause | Pain pattern | Tell-tale clues | STI? |
|---|---|---|---|
| PID | Deep | Pelvic pain, fever, foul discharge, bleeding between periods; often mild/silent | Yes (complication) |
| Genital herpes | Entry | Painful blisters/sores; flu-like first outbreak; often asymptomatic | Yes |
| Trichomoniasis | Entry/irritation | Itching, burning, fishy discharge; ~70% have no symptoms | Yes |
| Vaginal dryness | Entry | Friction/burning, low lubrication; common around menopause | No |
| Vaginismus | Entry | Involuntary muscle tightening; penetration blocked or painful | No |
| Endometriosis | Deep | Cyclical pain, painful periods, no infectious signs | No |
How it's tested
Testing depends on what's suspected: trichomoniasis is found with a NAAT (the preferred test — for example the Aptima T. vaginalis assay, with sensitivity around 95–100%) on a vaginal swab or female urine CDC, Trichomoniasis Tx Guidelines, 2021; herpes is confirmed when there's a sore by swabbing the lesion for type-specific NAAT or culture (swab-based tests work best on active lesions) CDC, Herpes Testing; and PID is diagnosed clinically — there's no single confirmatory test, so CDC advises a low threshold to treat pelvic or lower-abdominal pain plus cervical-motion, uterine, or adnexal tenderness CDC, PID Tx Guidelines, 2021. In practice that means a urine sample, a self-collected swab, or a quick exam, often free or low-cost at health departments, Planned Parenthood, and Title X clinics, with results usually back in a few days — get tested. If your exposure was recent, check when to test after exposure so you don't test too early to catch it.
What to do next
Because the symptoms overlap, you usually can't self-diagnose this; a test turns a guess into an answer. Get tested, then treat the actual cause: trichomoniasis and PID are treated with antibiotics, and herpes is managed with antiviral medication. Don't have sex until you and any partners are evaluated and treated, since untreated infection can keep passing back and forth.
Red flags — when to get seen urgently
Painful sex on its own is worth a visit, but get seen promptly — same day or the emergency room — if you have any of these:
- Severe lower-abdominal or pelvic pain, especially with fever or chills.
- Heavy or unexpected vaginal bleeding, or bleeding with fainting or dizziness.
- Foul-smelling discharge plus fever (a possible PID flare that can threaten fertility).
- Inability to urinate, or severe pain urinating with widespread genital sores.
- Pregnancy with pelvic pain and any abnormal bleeding.