References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Genital or oral sores can be caused by several STIs, and each needs a different treatment. The main culprits are herpes, syphilis, chancroid (rare in the UK) and LGV. Non-STI causes are also common. Proper testing gives the right diagnosis.
Here’s a practical guide.
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Common STI-Related Sores
| STI | Sore Type | Pain Level |
|---|---|---|
| Herpes | Cluster of small blisters, then ulcers | Painful |
| Syphilis (primary) | Single firm round ulcer (chancre) | Painless |
| Syphilis (secondary) | Mucous patches, condylomata lata | Usually painless |
| Chancroid | Painful ulcers (rare in UK) | Very painful |
| LGV | Small ulcer + swollen groin nodes | Variable |
| Granuloma inguinale | Painless progressive ulcer (very rare in UK) | Painless |
How to Tell the Types Apart
Herpes sores
- Start as small painful blisters
- Burst into shallow ulcers with red borders
- Crust and heal in 7-14 days
- Usually recur in the same area
Syphilis chancre
- Single, firm, round, painless
- Usually heals on its own in 3-6 weeks
- Can appear anywhere direct contact occurred
- Nearby lymph nodes may swell but are often painless
LGV
- Small painless ulcer that’s often missed
- Followed weeks later by painful swollen groin lymph nodes
- Rectal symptoms in MSM
Non-STI Causes of Sores
- Trauma or friction
- Allergic reactions
- Skin conditions (lichen sclerosus, Behçet’s disease)
- Aphthous ulcers
- Fungal infections
- Insect bites
Diagnosis
- Visual examination by a clinician
- Swab from the lesion for PCR (herpes or syphilis)
- Dark-field microscopy for early syphilis (in specialist centres)
- Blood tests for syphilis antibodies
- NAAT for LGV
Treatment by Cause
| Cause | Treatment |
|---|---|
| Herpes | Aciclovir / valaciclovir (antiviral) |
| Syphilis | Penicillin injection |
| LGV | Doxycycline 100mg twice daily for 21 days |
| Chancroid | Azithromycin or ceftriaxone |
When to Seek Help
- Any new genital or oral ulcer, especially after a sexual encounter
- Painless sores (easier to miss, often serious)
- Sores with swollen lymph nodes, fever or rash
- Sores that don’t heal in 2 weeks
- Recurring outbreaks
Read more: Identifying syphilis sores | Cold sores vs syphilis | LGV guide
Frequently Asked Questions
Can I tell what kind of sore I have by looking?
Not reliably. Several different conditions look similar. Testing confirms the cause.
Do all STI sores heal on their own?
Some do (syphilis chancres, herpes blisters), but the infection is still present and needs treatment. Never ignore a sore just because it heals.
Can I treat STI sores at home?
Over-the-counter products won’t cure STIs. A clinician needs to prescribe the correct treatment.
Related reading
- Abnormal Genital Discharge and Chlamydia
- Asymptomatic STIs: Silent Infections Explained
- Causes of Painful Sex and How to Treat It
- Cold Sores vs Syphilis Sores: How to Tell the Difference
- Common STI Symptoms in Women
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
