What Causes a False Positive on a Herpes Test?
Medically reviewed by Linda Girgis | MD, Girgis Family Medicine on August 21st, 2026.
False positive herpes test results occur in 5-10% of cases due to cross-reactivity with similar viruses. The most common cause is antibody interference from other herpes family viruses like varicella-zoster (chickenpox), Epstein-Barr virus, or cytomegalovirus. Laboratory errors, including sample contamination or equipment malfunction, can also trigger false positives. IgM tests have higher false positive rates than IgG tests because they detect more recent immune responses that may cross-react. Medical conditions affecting immune function, certain medications, and even pregnancy can influence test accuracy. If you receive a positive result, especially without symptoms, requesting confirmatory testing with a different method or laboratory can help verify the diagnosis.
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