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.
Early detection of herpes is possible when an active blister or ulcer is present — a swab from the lesion can identify the virus within days. Blood antibody testing exists but is less reliable for early detection because antibodies take weeks to develop after first infection. Understanding these differences helps you get the right test at the right time.
Here’s what to know.
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Types of Herpes Test
| Test | What It Detects | Best Used When |
|---|---|---|
| PCR swab | The virus itself | Active blister or ulcer present |
| Viral culture | Live virus from lesion | Less sensitive than PCR; rarely used now |
| Blood antibody test (type-specific) | Past exposure | No current lesion; detect past infection |
Swab Testing
Swabbing an active blister or ulcer is the most accurate way to diagnose herpes. PCR (polymerase chain reaction) testing identifies the virus directly and distinguishes HSV-1 from HSV-2. Accuracy is highest when:
- The lesion is fresh (within 48-72 hours of appearing)
- There’s clear fluid or blister material to sample
- The sample is sent quickly to the lab
Accuracy drops as lesions heal.
Blood Antibody Testing
Blood tests detect antibodies made by the body in response to herpes. Limitations:
- Antibodies take 3-12 weeks to develop after first infection
- Early in infection, blood tests can be negative while you’re contagious
- Can give false positives, especially at low levels
- Not routinely offered in the UK because results can be unclear
When Early Testing Makes Sense
- You have a visible blister or ulcer — get it swabbed promptly
- A partner has been diagnosed and you want clarity
- You’ve had severe flu-like symptoms with genital lesions (possible first outbreak)
When Blood Tests Are Appropriate
- To confirm past exposure when no current lesion is available
- Screening in specific clinical situations (pregnancy, couples planning pregnancy)
- To differentiate HSV-1 from HSV-2 antibodies
The UK Approach
UK sexual health services typically don’t offer routine herpes blood antibody testing for people without symptoms, because results can be difficult to interpret and cause anxiety without changing management. Testing is usually done when active lesions are present.
What to Do If You Suspect Herpes
- Contact a sexual health clinic promptly if you have a visible lesion
- Try to be seen while the lesion is fresh
- Avoid sex until you’ve been assessed
- Ask for PCR testing specifically
After Diagnosis
- Antiviral treatment (aciclovir) can be started
- Follow-up discussion about managing outbreaks
- Information about transmission prevention
- Support if you need it
Read more: What is herpes? | Do I have herpes? | Home herpes tests
Frequently Asked Questions
How soon can a swab detect herpes?
Immediately when a blister is present. PCR testing identifies the virus directly.
Can I get herpes tested without symptoms?
Blood antibody testing is possible but not routinely recommended in the UK due to interpretation difficulties.
Do home herpes tests work?
Swab kits for active lesions can be accurate. Antibody home kits have the same limitations as clinic antibody tests.
Related reading
- Comprehensive Test: Chlamydia, Gonorrhoea and Herpes
- Home Herpes Tests: A Guide to Testing at Home
- Herpes Blood Test: What It Shows
- Herpes PCR Test
- 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.
