Herpes Simplex Virus Type 1 Immunoglobulin G Antibody (Serum)

This test measures markers in your body that are linked to the herpes simplex virus (HSV), the virus that causes cold sores. Depending on the type of test, it may look for antibodies your immune system makes in response to the virus or for genetic material from the virus itself.

The test detects **IgG antibodies**—a type of protein your immune system produces in response to past exposure to HSV-1. These antibodies stay in your blood for years after infection, even if you no longer have active symptoms.

You might need this test if you have symptoms such as tingling, itching, or painful blisters around your lips or mouth, or if you have had close contact with someone who gets cold sores. It can also help your provider confirm a diagnosis or check for past exposure when your symptoms are unclear.

A doctor may order this test if you have recurrent cold sores, a history of HSV-1 infection, or if you’re being evaluated for immune-related conditions that could affect your ability to fight infections.

Before the test, your provider will explain how it works and answer any questions you have. Most versions of this test require little or no special preparation, but you may be asked to avoid eating or drinking for a short time if a blood sample is needed. Be sure to mention any medications, supplements, or active sores you have, since a sample may be taken directly from a lesion.

No special preparation is needed. You’ll provide a blood sample, usually drawn from your arm. The test is quick and typically done in a lab setting.

A positive result means markers of the virus were found, which may indicate a current or past infection depending on the type of test. A negative result suggests no signs of infection, though a very recent exposure may not show up yet. Occasionally results are inconclusive and repeat testing is needed. Your provider will explain what your specific result means and what steps to take next.

Results are qualitative (positive/negative) rather than numeric. A positive result means your body has likely encountered HSV-1 at some point. A negative result suggests no detectable antibodies, which may mean you’ve never been exposed or the test was taken too early after exposure.