You get shingles when the chickenpox virus wakes up inside your nerve cells

Shingles starts with a virus you likely caught years ago. After you recovered from chickenpox—whether as a child or later—the virus didn't leave your body. It went dormant in nerve tissue near your spine, where it can stay quiet for decades. Shingles happens when that dormant virus reactivates and travels along a nerve to your skin, causing a painful rash on one side of your body.

You cannot catch shingles from another person. You can only get it if you already had chickenpox or the chickenpox vaccine. The virus is already inside you; shingles is a reactivation, not a new infection from outside.

Key Takeaways

  • Shingles develops when the varicella-zoster virus, dormant in your nerve cells since chickenpox, reactivates and spreads along a nerve to your skin.
  • A weakened immune system is the most common reason the virus reactivates, which is why shingles is more frequent in people over 50 and those with certain medical conditions.
  • Physical stress, emotional stress, injury, or certain medications can trigger reactivation, though the exact trigger is often unclear.
  • You cannot catch shingles from someone else; you can only develop it if you previously had chickenpox or received the chickenpox vaccine.
  • About one in three people who had chickenpox will develop shingles at some point in their life.

Why the virus reactivates: immune system decline with age

The single strongest risk factor for shingles is age. Your immune system's ability to keep the dormant virus suppressed declines over time. People over 50 develop shingles far more often than younger adults. The risk rises sharply after age 60, and people over 80 have the highest rates.

This is why the virus can stay quiet for 20, 30, or 40 years after chickenpox, then suddenly reactivate. Nothing changed about the virus itself—your immune system's control over it weakened. This is also why shingles can recur: once the virus reactivates once, it can reactivate again later, though this is less common.

Medical conditions and medications that trigger reactivation

Anything that weakens your immune system increases the risk that dormant varicella-zoster will reactivate. People with HIV, especially those with low CD4 counts, have much higher rates of shingles. Cancer patients undergoing chemotherapy or radiation are at higher risk. Organ transplant recipients taking immunosuppressant drugs to prevent rejection face increased risk as well.

Certain medications suppress immune function as a side effect. Long-term corticosteroid use—such as prednisone taken for autoimmune conditions or severe asthma—can trigger reactivation. Some biologic drugs used for rheumatoid arthritis or inflammatory bowel disease carry this risk too. If you take medications that affect your immune system, discuss shingles risk with your doctor.

Physical and emotional stress as reactivation triggers

Severe physical stress can lower immune function enough to allow the virus to reactivate. Major surgery, serious injury, or a severe acute illness sometimes precedes shingles by days or weeks. Emotional stress—grief, major life changes, or prolonged anxiety—may also play a role, though the connection is less direct and harder to measure than with physical stress.

The stress does not cause shingles directly. Instead, stress hormones and inflammatory changes temporarily weaken immune control over the dormant virus. This is why shingles sometimes appears during or shortly after a period of high stress, though many people experience stress without developing shingles.

Local injury or irritation to nerve tissue

Injury to the skin or underlying tissue along a nerve path can sometimes trigger reactivation in that specific nerve. Trauma, surgery, radiation therapy, or even a severe sunburn in one area has been associated with shingles developing in that same location weeks or months later. The injury may alert the immune system to that area, or the inflammation from healing may create conditions where the virus reactivates.

This does not happen in most cases of local injury, and the mechanism is not fully understood. It is one of several possible triggers rather than a common cause.

Why the trigger is often unknown

In many cases, people develop shingles without any obvious trigger. They were not particularly stressed, had no recent illness or injury, and take no immunosuppressant medications. The virus simply reactivated, likely because of gradual, age-related immune decline that was not tied to any single event.

Researchers still do not fully understand why the virus reactivates in one person at one moment and remains dormant in another. The immune system's control over latent varicella-zoster is complex, involving multiple types of immune cells and proteins. A trigger may be present but invisible—a minor infection, a brief dip in immune function, or a change in the balance of immune cells that never causes noticeable symptoms.

Frequently Asked Questions

Can you get shingles more than once?

Yes, though it is uncommon. Most people who develop shingles have it once in their lifetime. Recurrence happens in roughly 1 to 5 percent of cases. People with severely weakened immune systems are more likely to have shingles more than once.

If someone in my house has shingles, can I catch it?

You cannot catch shingles itself. However, if you have never had chickenpox and have not been vaccinated, you can catch chickenpox from someone with active shingles. The virus spreads through direct contact with the rash. Once you recover from chickenpox, the virus becomes dormant in your nerve cells, and you could potentially develop shingles later in life.

Does the chickenpox vaccine prevent shingles?

The chickenpox vaccine (varicella vaccine) reduces the risk of shingles later in life, but it does not eliminate it. People vaccinated against chickenpox still develop shingles, though generally at lower rates than those who had natural chickenpox infection. A separate vaccine called Shingrix is designed specifically to prevent shingles in adults 50 and older.

Can stress alone cause shingles?

Stress alone does not cause shingles. You must already have the dormant varicella-zoster virus in your nerve cells from prior chickenpox or vaccination. Stress may lower immune function enough to allow reactivation, but only in someone who carries the virus. Stress is one possible trigger among several, not a direct cause.

Why do some people get shingles and others don't?

The difference comes down to immune function and individual variation in how well your body controls the dormant virus. Age, genetics, overall health, and specific immune system characteristics all play roles. Some people's immune systems maintain strong control over the virus throughout life; others' control weakens enough to allow reactivation. Researchers are still working to understand why this varies so much between individuals.