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.
PCR testing is the gold standard for diagnosing active herpes infection. It works by detecting the herpes simplex virus directly in a swab from a blister or ulcer. Compared to older methods like viral culture, PCR is more sensitive and provides faster, more reliable results. UK sexual health clinics use it routinely when herpes is suspected and an active lesion is present.
Here’s what to know.
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How PCR Testing Works
- A swab is taken from an active blister, ulcer or sore
- The sample is sent to a lab
- PCR amplifies any herpes DNA present
- The test identifies HSV-1 or HSV-2 (or both)
- Results within a few days
Best Time to Test
- While a blister is fresh — within 48-72 hours of appearing
- Before crusting or healing
- The earlier in the outbreak, the more accurate
Why PCR Is Preferred
| Method | Sensitivity |
|---|---|
| PCR swab | Very high when fresh |
| Viral culture | Lower; takes longer |
| Type-specific blood antibody | Variable; can be misleading |
| Direct visualisation | Not always reliable |
What Results Mean
Positive (HSV-1 or HSV-2)
Confirms active herpes infection at the swabbed site. Treatment is available.
Negative
No herpes detected at the swabbed site. Not all symptoms are herpes — other causes may need investigation.
What If There’s No Active Lesion?
Without a lesion, PCR can’t confirm or rule out herpes. Blood antibody testing is an alternative but less reliable. If you have intermittent symptoms, try to be seen during an outbreak for the most accurate diagnosis.
Where to Get Tested
- NHS sexual health clinics
- GP surgery
- Private clinics
- Some home test kits offer swab-based herpes testing
Treatment
- Antiviral medication (aciclovir, valaciclovir, famciclovir)
- Episodic treatment shortens outbreaks
- Suppressive treatment reduces recurrence and transmission
- Pain relief for discomfort
If Diagnosed
- Most people manage herpes well
- Outbreaks become less frequent over time
- Antivirals reduce severity
- Disclosure to partners is important
- Support resources are available
Read more: What is herpes? | Herpes early detection | Do I have herpes?
Frequently Asked Questions
How accurate is PCR for herpes?
Very accurate when an active lesion is swabbed promptly.
Can PCR distinguish HSV-1 and HSV-2?
Yes — type-specific identification is standard with PCR.
What if my swab is negative but I think I have herpes?
The lesion may have healed too much. Try testing during the next outbreak.
Related reading
- Comprehensive Test: Chlamydia, Gonorrhoea and Herpes
- Home Herpes Tests: A Guide to Testing at Home
- Herpes Blood Test: What It Shows
- Herpes Early Detection Testing
- Lab Test for Syphilis and Herpes
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.
