What Causes Shingles?

Shingles, also known as herpes zoster (HZ), is a viral disease that causes a painful skin rash. 

Typically, a shingles rash appears on only one side of the face or body. Most people will notice itching and pain before a rash with blisters that scabs over in 7–10 days. In severe cases, shingles causes a condition called postherpetic neuralgia (PHN)–persistent nerve pain in the area where the rash used to be. Rarely, shingles can lead to complications like pneumonia, vision or hearing loss, or encephalitis (inflammation of the brain). 

Shingles is caused by the varicella-zoster virus (VZV), which also causes chickenpox. After you have chickenpox—which may happen during childhood, but not always—the virus lies latent (inactive) in your body. However, it can be reactivated as shingles later in life, especially if your immune system is weakened. Anyone who has ever had chickenpox can get shingles, even if they didn’t have symptoms at the time.

In the United States, about 1 in 3 people will develop shingles at some point.

Who Gets Shingles?

Anyone who has had chickenpox or the chickenpox vaccine can get shingles. About 1 million people in the U.S. are diagnosed with shingles each year. However, some people are more likely to develop shingles than others.

The following may affect your chance of getting shingles and shingles-related health complications:

• Age: Your risk of shingles goes up as you age. Most people who get shingles are in their 50s or older, and around 50% of shingles cases are diagnosed in adults ages 60 and up. Up to half of people ages 85 and over will be diagnosed with shingles at some point.
• Sex: Shingles tends to be more common in women, making up nearly 60% of cases.
• Ethnicity: Some studies suggest shingles is more common in people of non-Hispanic white ancestry.

Is Shingles Genetic?

It’s still unclear how genetic factors affect your chance of developing shingles. But some research suggests that having certain genetic variants or a family history of shingles may increase your risk.

For example, in a 2016 meta-analysis of over 2000 reported cases of shingles, people with shingles were three times more likely to report a family history of it. What’s more, when people had more than one first-degree relative (a parent, sibling, or child) with a history of shingles, they were almost three times more likely to get it, compared to people with only one first-degree relative who had shingles.

Also, researchers have identified a potential gene variant for an immune molecule called the human leukocyte antigen (HLA). This gene is known as HCP5 (HLA Complex P5). Your HLA type can be tested with a blood test or cheek swab. Having certain variations of this gene may help prevent developing shingles—specifically in some people with European ancestry. However, more research is needed to explore other genetic variants that may be linked to your risk for shingles.

Risk Factors

Anyone who is immunocompromised (has a weakened immune system)—whether from certain health conditions or treatments—has a higher risk of developing shingles. They also have a higher risk of hospitalization, severe complications, and (rarely) death from shingles.

The following are risk factors for shingles and related complications:

Cancer

People who have or recently had cancer are at a greater risk of developing shingles and are more likely to be hospitalized for severe complications. The risk of shingles is greatest in the year after a cancer diagnosis. 

Studies have found that people with cancer are 40% more likely to get shingles. Particularly, people with blood cancer, such as leukemia or lymphoma, have a higher risk compared to those with solid organ cancer–such as breast cancer or colon cancer.

Human Immunodeficiency Virus (HIV)

People with human immunodeficiency virus (HIV) are approximately 12–17 times more likely to get shingles than people without HIV. HIV severely weakens the immune system’s ability to fight viruses and other invaders. 

If you have shingles and present with uncommon symptoms, your healthcare provider may test you for HIV.

Diabetes

Type 1 or type 2 diabetes– are conditions that limit your body’s production of insulin (a hormone that regulates blood sugar). People with diabetes are 1.6 times more likely than people without diabetes to develop shingles.

Immunosuppressive Treatments

Any medication or treatment that suppresses your immune function may put you at a greater risk of getting shingles.

These treatments may include immunosuppressants (such as steroids), which are a type of medication that prevent immune system activity and are often used to treat autoimmune disorders (conditions that cause your immune system to be over-reactive, attacking certain parts of your body). If you’re undergoing chemotherapy or radiation therapy, or if you recently had an organ or bone marrow transplant, you may also be at greater risk for developing shingles.

Physical Trauma

There may be a link between getting shingles and recent physical trauma. A 2013 study found that people with shingles were over three times more likely to have experienced physical trauma in the week before their diagnosis. In general, the risk for developing shingles was higher for physical trauma involving open wounds, sprains or strains, and head or neck injury.

Stress

Some studies indicate that stressful events could increase the risk of getting shingles, especially if you’re over 50 years old. However, research is ongoing.

A Quick Review

Shingles, also called herpes zoster, is a painful skin rash caused by a reactivation of the varicella-zoster virus—the virus that causes chickenpox. You can get shingles if you’ve ever had chickenpox or the chickenpox vaccine. You can get shingles at any age, but you’re more likely to if you’re over 50 years old. Women may also be somewhat more likely to develop shingles. 

Other risk factors for shingles include having other conditions like diabetes, cancer, and HIV, as well as experiencing stress and physical trauma. People who are immunocompromised are also more at risk.