Shingles, also called herpes zoster, is a disease caused by a reactivation of the varicella-zoster virus that leads to chickenpox. The virus can remain dormant in your nerve cells for decades without presenting any symptoms.

Shingles most commonly occurs in people over the age of 50. About 1 in 3 people in the United States will develop it in their life. The main symptom of shingles is a painful rash on one side of your body that usually goes away after 2 to 4 weeks.

The rash can appear on any part of your body, but it typically appears on one side of your trunk or torso. The location of a shingles rash depends on which nerve in your body the virus spreads from. Usually, the rash is contained in one or two areas of your skin called dermatomes.

Keep reading as we take a look at how and why shingles follows along nerve paths.

Shingles is caused by a reactivation of the virus that causes chickenpox. Only people who’ve had chickenpox or chickenpox vaccines can develop shingles. Having a chickenpox vaccine can lead to shingles because the vaccine contains the virus that causes chickenpox.

Shingles isn’t contagious, but people who have not had chickenpox can develop chickenpox if they come in contact with open blisters of somebody with shingles.

After your body fights off a chickenpox infection, the herpes zoster virus remains dormant in your cranial nerves and spinal ganglia until it becomes reactivated. Spinal ganglia are nerve cells that connect your spinal cord to nerves in your body and limbs.

The virus reactivates when your immune system is no longer able to suppress it. Reactivation most commonly occurs in older adults because the immune system tends to get weaker with age, as well as in people with suppressed immune systems.

Once the virus is active, it usually spreads down sensory nerve fibers that lead from your spinal cord to your skin. These nerves carry sensory information like feelings of pain, itchiness, or pressure from your skin to your spinal cord and brain.

Once the virus gets to the end of these sensory nerves, it reaches your skin and usually leads to a rash. This rash often shows up in one or two nearby areas of skin called dermatomes.

Herpes zoster, Shingles, dermatomes, shingles reactivation, nerve paths that shingles followShare on Pinterest
Shingles Dermatomes. Illustration by Alexis Lira.

You have 31 spinal nerves on each side of your body that help send information between your body and spine. Each of these nerves is associated with a dermatome except for the C1 spinal nerve in your neck.

A dermatome is an area of your skin where the sensation is supplied by one spinal nerve.

For example, the C5 spinal nerve found on the right side of your body is responsible for delivering sensory information from your right collarbone and upper shoulder to your spinal cord and brain. All the skin in this region is one dermatome.

Shingles rashes tend to form along one or two dermatomes on one side of your body. Their location depends on which nerve the virus spreads from. The rash doesn’t cross the midline of your body because each spinal nerve supplies sensory information only for the left or right side of your body.

As the herpes zoster virus travels along your sensory nerves, it can cause damage and inflammation that leads to pain, even after your rash disappears.

Postherpetic neuralgia

The most common long-term complication of shingles is a condition called postherpetic neuralgia.

Postherpetic neuralgia refers to pain or intense itchiness that lasts after a shingles rash heals. It’s estimated that 10 to 18 percent of people with shingles develop postherpetic neuralgia.

Most people recover from postherpetic neuralgia within a year, but in some cases, it can be permanent.

Motor nerve damage

The herpes zoster virus can also infect the nerves that help you move your muscles. It’s thought that about 0.5 to 5 percent of people with shingles develop a condition called segmental zoster paresis. This condition leads to weakness in the muscles around the shingles rash.

Cranial nerve damage

In some cases, the herpes zoster virus affects one of the major nerves in your head called cranial nerves. Less than 1 percent of shingles cases affect cranial nerve VII (facial nerve) and lead to a condition called Ramsay Hunt syndrome.

This syndrome can cause symptoms such as:

Damaged sensory nerves can lead to a condition called postherpetic neuralgia, in which pain persists after your rash disappears.

Four types of medications are used to treat pain from postherpetic neuralgia. Sometimes, a combination of medications is used.

Anticonvulsants

Anticonvulsants, such as gabapentin and pregabalin, are approved by the Food and Drug Administration (FDA) to treat postherpetic neuralgia. These drugs bind to calcium channels and influence neurotransmitter release to relieve pain.

Antidepressants

A wide range of antidepressants may be used at low dosages to help manage pain. One group of antidepressants commonly used for this purpose is tricyclic antidepressants. These drugs inhibit the reuptake of serotonin and norepinephrine.

Opioids

Opioid medications are effective at treating nerve pain, but doctors are often reluctant to prescribe them unless other options fail. Opioids are often the last resort because of their potential to lead to dependence or overdose. Prescription opioids include:

  • hydrocodone
  • oxymorphone
  • morphine
  • codeine
  • fentanyl

Topical local anesthetics

Two types of creams are commonly used to help manage nerve pain. Lidocaine is FDA-approved specifically for treating postherpetic neuralgia. Capsaicin cream is available over the counter and has been found to be somewhat effective, but many people experience burning pain while putting it on.

Postherpetic neuralgia can be very painful, but here are some things you can do at home to lessen your discomfort:

  • wear comfortable clothing made from cotton or silk to reduce irritation
  • apply an ice pack wrapped in a towel to the sore area
  • eat a balanced diet
  • get plenty of rest
  • minimize stress
  • exercise regularly

The same virus that causes chickenpox can also cause shingles. The virus can remain dormant in your nerves for decades after chickenpox infection before becoming active again.

Once reactivated, the virus spreads to your skin by traveling down your nerves. The area that your rash appears on depends on which nerve the virus travels from.

Shingles is thought to appear when your immune system is no longer able to suppress the virus. Keeping your immune system healthy by eating a balanced diet, exercising regularly, and minimizing stress may help reduce your chance of developing shingles. You can also get one of two FDA-approved shingles vaccines.