How Chickenpox Is Diagnosed

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

chickenpox diagnosis
© Verywell, 2018 

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 healthcare provider 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 healthcare provider can diagnose it by simply looking at the rash. Your healthcare provider 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 healthcare provider may have you go immediately back to an exam room rather than waiting in the lobby.

Chicken Pox Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Child

When Additional Testing Is Needed

When would your healthcare provider 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 healthcare provider 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 chance of miscarriage and birth defects. In most cases, there's nothing to worry about. It's riskier 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 healthcare provider 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 healthcare provider 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 healthcare provider suspects chickenpox, but you don't have the "typical" rash.

In these cases, your healthcare provider 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:

Frequently Asked Questions

  • Is it dangerous for adults to get chickenpox?

    Yes, adults and older teens tend to have more chickenpox lesions and are more likely to develop liver, respiratory, neurologic, or other complications, such as pneumonia. While virtually all adults in the U.S. have had chickenpox at some time by age 40, the same is not necessarily true in other parts of the world.

  • What type of virus causes chickenpox?

    The varicella zoster virus causes chickenpox. It may also, later in life, re-emerge as shingles.

  • What test is used to diagnose chickenpox?

    A blood test is often used to identify the presence of varicella-zoster virus, which causes chickenpox. A polymerase chain reaction, or PCR, test is the newest, most reliable form of diagnosis, though a blood test is also considered reliable.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Chickenpox (Varicella): Signs and Symptoms.

  2. Freer G, Pistello M. Varicella-Zoster Virus Infection: Natural History, Clinical Manifestations, Immunity and Current and Future Vaccination StrategiesThe New Microbiologica. 2018 Mar 2;41(1).

  3. Centers for Disease Control and Prevention. Chickenpox (Varicella): Vaccination.

  4. Singh A, Parkash S, Gupta SK, Soni RK. Severe Varicella Pneumonia in Adults: Seven Years' Single-center Experience from IndiaIndian J Crit Care Med. 2018;22(3):162–167. doi:10.4103/ijccm.IJCCM_495_17

  5. Centers for Disease Control and Prevention. Chickenpox (Varicella). Interpreting Laboratory Tests.

By Angela Palmer
Angela Palmer is a licensed esthetician specializing in acne treatment.