Short answer
Genital-sore evaluation is pattern-plus-laboratory medicine with a time limit: lesion characteristics prioritize, fresh NAAT swabs plus syphilis serology confirm, structured history screens mimics. Completed promptly, because healing erases diagnostic yield daily while infections persist regardless.
The evaluation that happens on day two outperforms the evaluation on day twelve even with identical thoroughness.
Continue with Genital Sores: Possible Causes and Next Steps and Genital Rash: Possible Causes and When to Get Care for the directly connected guidance.
Advertisement
Need a test? STDTest.online is education-only and does not provide testing. The banner above is a paid advertisement for an independent testing service. We may earn a commission if you use it, at no extra cost to you. Always confirm current prices, accreditation, and privacy terms on their website before ordering.
See Tests & Prices →Lesion mapping: reading the sore
Clinicians document number (single suggests chancre; grouped suggests herpes; multiple ragged suggests chancroid), distribution, pain level (painless firm versus painful soft is the classic syphilis-herpes split. Suggestive, never conclusive), edge character (rolled, undermined, clean), base (foul, firm, necrotic), lymph nodes (tender, firm, groove sign of LGV), and evolution timeline.
Each feature weights differentials without concluding them; photography tracks changes objectively across visits.
Laboratory core that confirms
Unroofed-lesion NAAT with HSV typing. Intact blister fluid tests best, so patients should avoid popping, picking, or creaming sores beforehand.
Syphilis treponemal/non-treponemal cascade regardless of suspected cause (syphilis mimics everything).
HIV screening by risk profile.
Chancroid/LGV workups where epidemiology fits (travel, networks, bubo patterns).
Coinfection is common enough that single-organism testing under-serves ulcer patients.
Mimic screening beyond STIs
Oral ulcer history (Behçet’s disease pairs genital and oral aphthae with eye/joint features).
Bowel symptoms (Crohn’s disease produces fissured genital ulcers).
Medication timelines (fixed drug eruptions recur at the same spot with each dose. The drug history is diagnostic).
Trauma and friction contexts.
Biopsy thresholds for atypical persistent lesions. The backstop catching malignancy and autoimmune disease that swabs and serology miss.
While awaiting results
Complete abstinence from all sexual activity (sores shed regardless of barriers).
No topical steroids or antibiotics obscuring morphology.
Partner-notification preparation started now. Exposure disclosure immediately, specifics after results.
Pregnancy assessment where relevant, since lesions near delivery change obstetric planning.
When to seek care
Same-day for new sores. Diagnostic yield decays with healing, and first presentations always warrant full workups.
Urgently for urinary retention, extensive tissue death, rapidly spreading pain and swelling, or immune suppression with severe lesions.