What Causes Shingles?

Varicella zoster virus reactivation isn't well understood but there are theories

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Shingles is caused by the reactivation of the varicella zoster virus (VZV), which, when it first infects the body, causes chickenpox and then goes into hiding in the nervous system. Why the virus re-emerges isn't entirely understood, but there are theories. 

Shingles is most common in older people, but anyone with the varicella zoster virus is at risk. In fact, reduced immunity is considered the biggest risk factor for shingles. Researchers believe that stress could also play a role for some people.

shingles risk factors
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Shingles is an especially unpleasant illness. It causes a painful and unsightly skin rash, as well as potential long-term complications, the most common one being a condition known as postherpetic neuralgia (PHN).

PHN is characterized by a burning sensation where the shingles rash once was. That's why it's important to understand what causes shingles, what the risk factors are, and how to protect yourself.

Shingles Causes

After you recover from chickenpox, the symptoms disappear but the varicella virus retreats to cells in your nervous system, where it can hang out for decades without causing problems.

What prompts the varicella virus to reactivate and cause shingles isn't entirely understood. The virus is a member of the same family of microbes that cause herpes infections, such as genital herpes and cold sores, which also tend to come and go, so it's not surprising that varicella would behave similarly.

The big difference is, while herpes infections can recur multiple times, most people only experience shingles once (although it can come back).

The viral reactivation seems to have two main causes: a weakened immune system and stress.

Weakened Immune System

There is a clear association between shingles and weakened immunity to infection. Even though the varicella virus is not invading the body for the first time, the immune system still is responsible for keeping it at bay.

Sometimes, however, it's unable to do that. What this means is that the varicella virus, which after causing the chickenpox rash in the skin had traveled to ganglia in the nervous system, becomes active again and heads back to the skin.

Since it travels along the nervous system, the rash stays on one side of the body and appears in the shape of a strip or band that aligns with the shape of the nerves below the skin.


There's a long-held hypothesis that chronic stress or even a single episode of emotional distress can trigger the dormant varicella virus to become active again and bring on a shingles outbreak.

Given that stress often is linked to any number of changes in health, including gastrointestinal problems, migraines, and eczema, this notion is not at all far-fetched.

In fact, some evidence supports it. An often-cited 1998 study of otherwise healthy adults over 60 found that those who had had shingles were more than twice as likely to have had a negative life event within six months of the outbreak as peers who didn't have shingles.

When asked about events within the past two to three months specifically, those in the shingles group reported the same amount of negative life events as their unaffected counterparts. This suggests that perceiving an event as stressful, rather than the event itself, may be linked to increased rate of shingles.

More recent research has largely supported this concept. Some have taken this to mean that the overall perception of stress and the ability to cope with it may add to the underlying factors that create the perfect storm for a shingles outbreak.

Shingles Risk Factors

Since compromised immunity is the most common trigger for a latent varicella virus to become active, any factor associated with a weakened immune system can increase the risk of shingles. Important risk factors for shingles include:

  • Being 50 or over: With age, there is a natural decline in cell-mediated immunity.
  • Infection from human immunodeficiency virus (HIV): Although most people who develop shingles have the infection just once, it's not uncommon for someone with HIV to have recurrent shingles infections.
  • A chronic medical condition: Cancer (especially leukemia or lymphoma) or diabetes are examples.
  • Medication that suppresses the immune system: Some examples of these include chemotherapy drugs and systemic steroids, such as prednisone.
  • Having an organ transplant: The medications that are necessary for preventing organ rejection suppress the immune response. 

Note that many of these risk factors are as likely to apply to young people and children as they are to older people. So, even though shingles often is regarded as an illness of advancing age, this isn't always the case.

Virus Reactivation and Symptoms

When the virus re-emerges, it typically reactivates in clusters of nerve cells in the peripheral nervous system called a sensory ganglion. The ganglia most likely to host varicella are those in the cervical, thoracic, and lumbar spine.

Varicella also often affects the trigeminal ganglion, which provides sensation to the face. As its name suggests, this particular clump of nerves has three branches. The one associated with eye function, the ophthalmic branch, is 20 times more likely than the other two to be affected.

Since the nervous system consists of tree-like branches of nerves, the blisters will follow the particular path of the nerves affected. That's why a shingles rash often resembles a swath of blisters in a very specific area, rather than spread all over the body (as in chickenpox).

The area with the particular nerve cells in which the virus reawakens is where the shingles symptoms—extreme pain and rash—will be concentrated.

This photo contains content that some people may find graphic or disturbing.

herpes zoster on thigh

DermNet / CC BY-NC-ND

Along with the rash, symptoms of shingles may include:

  • Fever
  • Chills
  • Headache
  • Upset stomach

For several days before the rash appears, you may have tingling, itching, or pain in the affected area.

When to See a Healthcare Provider

  • If you suspect shingles
  • Within 3 days of getting the rash, to prevent lasting nerve pain
  • If the rash and pain are near an eye, which can cause permanent eye damage
  • If you're over age 60 due to an increased risk of complications
  • If you have a weakened or suppressed immune system or someone close to you does

Shingles Doctor Discussion Guide

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

Doctor Discussion Guide Old Man


Shingles is best prevented with a vaccine. Called Shingrix, this vaccine is considered safe and 90% effective at preventing the disease. It's given in two doses and is available in medical offices and some pharmacies.

You should get the shingles vaccine if:

  • You're over 50
  • You've had chickenpox, the chickenpox vaccine, or shingles
  • You haven't had chickenpox
  • You got the prior shingles vaccine (Zostavax)

Don't Get the Shingles Vaccine If:

  • You currently have shingles
  • You're sick or have a fever
  • You had an allergic reaction to a previous dose of this vaccine

Avoidance is an important part of prevention, too. If you haven't had chickenpox or a chickenpox vaccine:

  • Avoid people who have chickenpox so you don't catch it.
  • Avoid people who have shingles. You could catch chickenpox (but not shingles) from them.

Frequently Asked Questions

  • Is shingles contagious?

    Not exactly. You can't catch shingles from someone else. Shingles is caused by the varicella-zoster virus that re-emerges after you've had chickenpox. However, if you have shingles, you can spread the virus and cause someone to get chickenpox if they've haven't had it before or been vaccinated.

  • Can you get shingles without having chickenpox?

    No, you can't get shingles if you've never had chickenpox. If you've had the chickenpox/varicella vaccine, you're also protected from getting shingles.

  • What are the first signs of having shingles?

    The first sign is often itching, tingling, or pain in a confined area. The rash may appear there after a few days.

  • How many times can you get shingles?

    While it's rare to get them more than once, it's possible to come down with shingles multiple times. That's why the vaccine is recommended even for people who've had shingles before.

19 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.
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Additional Reading

By James Myhre & Dennis Sifris, MD
Dennis Sifris, MD, is an HIV specialist and Medical Director of LifeSense Disease Management. James Myhre is an American journalist and HIV educator.