Short answer
Vulvar sores demand same-day evaluation because STI causes (herpes, syphilis, chancroid) and systemic mimics (Behçet’s disease, Crohn’s disease, Lipschütz ulcers, fixed drug eruptions, trauma, malignancy) overlap totally in appearance. Only fresh-sore testing plus structured history sorts them.
Healing proves nothing (chancres and herpes both remit spontaneously) while swab accuracy decays daily, so speed is diagnostic yield and delay is diagnostic loss.
Continue with Genital Sores: Possible Causes and Next Steps and Genital Sores: Causes and Evaluation for the directly connected guidance.
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See Tests & Prices →STI causes with their classic (unreliable) faces
- Herpes: grouped painful blisters becoming shallow ulcers, often with burning urination or groin tenderness.
- Primary syphilis: solitary painless firm chancre. The painlessness causing dangerous delay.
- Chancroid (rare): soft painful ragged ulcer with tender nodes.
- LGV: transient sore long before groin swelling.
- HIV seroconversion ulcers: occasionally.
Memorize these as orientations; real sores break textbook rules constantly, and coinfection means even a “classic” sore deserves full testing.
Non-STI causes that fool confidently
- Behçet’s disease: recurrent oral plus genital ulcers with eye inflammation or joint pain. Systemic patterns no STI produces.
- Crohn’s vulvar disease: fissured “knife-cut” ulcers with bowel symptoms.
- Lipschütz ulcers: acute, painful, large ulcers in adolescents, usually post-viral (EBV-associated), self-limited but terrifying. Evaluated identically to STI sores at first presentation.
- Fixed drug eruptions: same-spot recurrence with each drug dose. The medication timeline is diagnostic.
- Trauma and friction, hidradenitis suppurativa, lichen planus erosions, pemphigoid disorders.
- Vulvar malignancy: persistent atypical non-healing lesions, mainly older patients. Biopsy thresholds, never reassurance.
Evaluation protocol that misses nothing
Lesion examination with mapping and photography.
Fresh NAAT swabs with HSV typing. Intact blister fluid tests best, so no popping, picking, or creams beforehand.
Syphilis and HIV serology regardless of suspected cause. Medication review for fixed-eruption patterns.
Systemic review: bowel symptoms (Crohn’s), eye/joint symptoms (Behçet’s), recent viruses (Lipschütz), immune status.
Biopsy for atypical or persistent lesions. The backstop catching malignancy and autoimmune disease.
While awaiting results
Complete abstinence including oral sex.
Gentle cleansing, no topical steroids or antibiotics obscuring morphology.
Partner-notification preparation (exposure disclosure now, specifics after results).
Pregnancy assessment where relevant. Lesions near delivery change obstetric planning.
When to seek care
Same-day for any new vulvar sore. Swab yield decays with healing, and first presentations always get full STI workups regardless of suspected cause.
Urgently for urinary retention, extensive spreading, black/necrotic tissue, or pregnancy with lesions.