A doctor can usually diagnose shingles based on your symptoms. But in some cases, such as when shingles doesn’t cause a rash, other testing may be necessary.

Shingles results from reactivation of the varicella-zoster virus (VZV), the virus that causes chickenpox. The condition usually causes a painful and distinctive rash on one side of the body.

Doctors typically diagnose shingles by a physical examination, but that’s not always conclusive. Sometimes, shingles doesn’t cause a rash. Other conditions might also cause physical symptoms similar to the blisters and lesions associated with shingles.

Doctors can use other testing methods to diagnose shingles if a case is mild or has an unusual presentation.

Usually, a doctor can diagnose shingles from the symptoms alone. The common symptoms of shingles are:

  • fever, pain, tingling, and itching before the rash appears
  • rash in a single stripe on one side of the body
  • headache
  • chills
  • upset stomach

Some people have unusual presentations of shingles, so a doctor might recommend testing for the presence of the VZV. A polymerase chain reaction (PCR) test is the most useful test to detect the presence of VZV DNA.

To run a PCR test, a healthcare professional takes a fluid sample from a shingles blister. They might take a blood sample to perform a PCR test if your infection is widespread or affects your eye.

When might I need a shingles test?

Tests for shingles are typically only necessary if the virus presents in an unusual way, which can include:

  • mild symptoms
  • no rash
  • a widespread rash

Such cases are more likely in:

  • children
  • young adults
  • people with weakened immune systems
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Other ways to diagnose shingles exist besides a PCR test. While less useful than a PCR test, doctors may use them if PCR testing is unavailable.

  • Tzanck smear: This requires fluid or a scraping from a blister. It’s less sensitive than a PCR test but might detect other viruses that cause symptoms.
  • Antibodies in blood: Some sources recommend the immunoglobulin G (IgG) antibody test only to check for immunity to shingles and not to diagnose an active case. The immunoglobulin M (IgM) antibody is another possible test, but only when the virus is active.
  • Direct fluorescent antibody (DFA): This also requires a blister scraping. It offers quick and specific results but is less sensitive than a PCR test.

A shingles rash is usually distinctive enough for a doctor to make a diagnosis. But sometimes, it might resemble a different skin condition, such as:

In the case of zoster sine herpete (ZSH), aka silent shingles, the infection doesn’t cause a rash. This often results in misdiagnosis. Without timely treatment, ZSH can lead to serious complications like postherpetic neuralgia.

Here are some common queries people have about diagnosing shingles.

What are the early symptoms of shingles?

Before you develop a shingles rash, you might experience pain, itching, or tingling on the skin area where you get the rash. You can also get a headache, experience light sensitivity, or generally feel unwell.

What does a mild case of shingles look like?

Mild shingles might only cause minor pain or itching. You might have fewer lesions (blisters) or no blisters at all. People with more severe shingles can have extreme skin sensitivity, experiencing pain even from just a gentle touch.

Can blood work detect shingles?

A blood test can detect antibodies for the shingles virus. However, routine blood testing won’t necessarily detect shingles. A healthcare professional can usually order a specific test for shingles.

Blood testing for shingles is less reliable than PCR testing.

What is silent shingles?

Silent shingles refers to when the condition doesn’t cause a rash. It’s still a result of the reactivation of VZV and can cause many of the same complications. Because there’s no characteristic rash, it can be difficult to diagnose based on a physical examination alone.

Doctors can diagnose most cases of shingles based on examining symptoms alone. But in some cases, people have a mild case with fewer physical symptoms or a type of shingles that doesn’t cause a rash. In these cases, a doctor might perform other tests, such as a PCR test.