How Chickenpox Is Diagnosed

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chickenpox diagnosis
© Verywell, 2018 

Chickenpox is typically easy to diagnose by a physician through a simple examination of the rash. If there's any uncertainty, it can be confirmed with lab testing.

Self-Checks/At-Home Testing

Just a few decades ago, the chickenpox was an incredibly common illness. Nearly everyone came down with it at some point during childhood.

Because it was so common, most people were familiar with what chickenpox looked like and often diagnosed themselves. You would suspect the chickenpox if you (or your child) develop raised, red bumps that progressed to blisters, especially if this rash developed a few days after having a fever or feeling unwell.

Changes With the Vaccine

Since the introduction of the vaccine, most children today will never get the chickenpox. You've likely never seen a chickenpox rash before. Being unfamiliar with the rash makes it difficult to self-diagnose.

Other skin rashes can look very similar to chickenpox, though, so it is important to have yourself checked over by a doctor if you have an itchy, raised rash.

Labs and Tests

In the majority of cases, you won't need to have any testing done to get an official diagnosis of chickenpox. Your doctor can diagnose it by simply looking at the rash. Your doctor will also ask about any other symptoms you or child have had and when they started, as well as if you have been exposed to the chickenpox (if known).

When you make your appointment or arrive at the clinic, be sure to tell the front office staff that you think you may have the chickenpox. Many offices, especially pediatric offices, have a specific protocol to limit exposing others to the virus. For example, your child's pediatrician may have a separate waiting area, or your doctor may have you go immediately back to an exam room rather than waiting in the lobby.

When Additional Testing Is Needed

When would your doctor opt for additional testing? There are a few cases.

  • Severity. You have a very mild case of chickenpox. In mild cases, the rash often doesn't look like the "typical" chickenpox rash. You may just get small red bumps that never blister. These bumps resemble insect bites or an allergic reaction, so your physician will want to confirm what you're experiencing is truly the chickenpox.
  • Pregnancy. You're pregnant and think you may have the chickenpox or have been exposed to it. There is a  very slight chance of miscarriage and birth defects. In most cases, there's nothing to worry about. It's riskier is if you have chickenpox immediately before you deliver because you can pass the disease on to your newborn. It's very important you consult with your doctor if you're pregnant and think you have the chickenpox.
  • Vaccinations. You, or your child, have been vaccinated for the chickenpox but have a rash that resembles the illness. Even if you have been vaccinated it's still possible to get chickenpox. This is more likely if you've only had one vaccination, less so if you've had two. But, in both cases, it is still fairly uncommon. If you've been vaccinated but your doctor still suspects chickenpox it's likely you'll have a blood test or viral culture done to confirm. The good news is if you've been vaccinated and still come down with the chickenpox, it will likely be a mild case that resolves fairly quickly.
  • Atypical symptoms. Your doctor suspects chickenpox, but you don't have the "typical" rash.

In these cases, your doctor may perform the following tests.

Blood Work

A blood test can also be done to check to see if you have an active chickenpox infection or if you are immune to the disease. A small amount of blood is drawn and sent to a lab to check for varicella zoster virus antibodies. The varicella-zoster virus is the virus that causes chickenpox.

Viral Culture

Sometimes a viral culture is done instead of a blood test. A sample of fluid is taken from a blister and sent to the lab, where the specimen is allowed to grow. After a period of time, it's checked for the varicella-zoster virus.

You won't get immediate results from either of these tests, though the blood test is faster than a viral culture. With a viral culture, the results may not come back until the virus has already run its course.

Differential Diagnoses

There are other things that cause a raised, itchy red rash or skin blisters. These skin problems cause rashes that can be confused for chickenpox:

Remember that your physician, in most cases, can easily diagnose chickenpox. If it's not chickenpox, your doctor can help you treat that too.