Shingles (herpes zoster) is infection that results from reactivation of the varicella-zoster virus, the virus that causes chickenpox.
Chickenpox and shingles are caused by the varicella-zoster virus (another member of the herpesvirus family, herpesvirus type 3—see Herpesvirus Infection Overview):
During chickenpox, the virus spreads in the bloodstream and infects collections of nerve cells (ganglia) of the spinal or cranial nerves. The virus remains in the ganglia in a dormant (latent) state. The virus may never cause symptoms again, or it may reactivate many years later. When it reactivates, the virus travels down the nerve fibers to the skin, where it creates painful sores resembling those of chickenpox. This outbreak of sores (shingles) almost always appears on a strip of the skin over the infected nerve fibers and only on one side of the body. This strip of skin, the area supplied by nerve fibers from a single spinal nerve, is called a dermatome (Fig. 2: Dermatomes). Adjacent dermatomes may also be infected.
Unlike herpes simplex virus infections, which can recur many times, there is usually only one outbreak of shingles in a person's lifetime. However, people with a weakened immune system may have shingles more than once. They may also have unusual sores, sores on many dermatomes, or sores on both sides of the body.
Shingles may develop at any age but is most common after age 50.
Most often, the reason for reactivation is unknown. However, reactivation sometimes occurs when the immune system is weakened by another disorder, such as AIDS or Hodgkin lymphoma, or by use of drugs that suppress the immune system (for example to prevent rejection of a transplanted organ). The occurrence of shingles does not usually mean that the person has another serious disease.
Symptoms and Complications
During the 2 or 3 days before shingles develops, most people have pain, a tingling sensation, or itching in a strip of skin (a dermatome) on one side of the body. Clusters of small, fluid-filled blisters surrounded by a small red area then develop on the strip of skin. The blisters occur only on the limited area of skin supplied by the infected nerve fibers. Most often, blisters appear on the trunk, usually on only one side. However, a few blisters may also appear elsewhere. Typically, blisters continue to form for about 3 to 5 days. The affected area is usually sensitive to any stimulus, including light touch, and may be very painful. Symptoms are usually less severe in children than in adults.
The blisters begin to dry and form a scab about 5 days after they appear. Until scabs appear, the blisters contain varicella-zoster virus, which, if spread to susceptible people, can cause chickenpox. Blisters that cover large areas of skin or persist for more than 2 weeks usually indicate that the immune system is not functioning normally.
The affected skin, especially in older people and in people with a weakened immune system, may become infected by bacteria. Scratching the blisters increases this risk. Bacterial infections increase the risk of scarring.
One episode of shingles gives most people lifelong immunity from further attacks. Fewer than 4% of people have more than one episode. Scarring or hyperpigmentation of the skin, which can be extensive, may occur, but most people recover without lasting effects. A few people, more commonly older people, continue to have chronic pain in the area (postherpetic neuralgia).
The part of the facial nerve leading to the eye can be affected, causing pain and blisters on and around the eye and sometimes on the tip of the nose. This infection (called herpes zoster ophthalmicus—see Herpes Zoster Ophthalmicus) can be serious. If the disorder is not treated adequately, vision may be affected.
The part of the facial nerve leading to the ear may also be affected. This infection (called herpes zoster oticus, or Ramsay Hunt syndrome—see Herpes Zoster Oticus) can cause pain, partial paralysis of the face, and hearing loss.
Chronic pain in areas of skin supplied by nerves infected with herpes zoster is called postherpetic neuralgia. Exactly why the pain occurs is not well-understood. However, it does not indicate that the virus is actively reproducing (replicating).
Postherpetic neuralgia occurs most often in older people: 25 to 50% of people who are older than 50 years and who have had shingles also have postherpetic neuralgia. However, only about 10% of people with shingles develop postherpetic neuralgia.
The pain may be constant or intermittent, and it may worsen at night or in response to heat or cold. Few people have severe pain. But sometimes the pain is incapacitating.
In most instances, the pain subsides within 1 to 3 months. But in 10 to 20% of people, the pain persists for more than 1 year. It rarely persists more than 10 years.
People who suspect they have shingles should see a doctor right away because to be effective, treatment must be started early. Doctors ask them to precisely describe the location of the pain. Pain in a vague band on one side of the body suggests shingles. If characteristic blisters appear in the typical pattern (on a strip of skin representing a dermatome), the diagnosis is clear.
Rarely, doctors take a sample from the blisters to be analyzed or do a skin biopsy to confirm the diagnosis.
Preventing chickenpox by vaccinating children and adults who do not have immunity with the varicella vaccine is recommended (see Prevention).
A vaccine to prevent shingles is recommended for healthy people aged 60 or over, regardless of whether they have had chickenpox or shingles. This vaccine decreases the chance of getting shingles by one half and decreases the chance of getting postherpetic neuralgia by two thirds. If shingles develops in people who have been vaccinated, it is less severe than in those who have not been vaccinated.
When shingles occurs, taking antiviral drugs reduces the risk of developing postherpetic neuralgia.
Several antiviral drugs are effective in treating shingles. Oral antiviral drugs such as famciclovir or valacyclovir are often given, particularly to older people and to people with a weakened immune system. Acyclovir is sometimes used. The drugs should be started as soon as shingles is suspected, before blisters appear if possible. The drugs are likely to be ineffective if started more than 3 days after blisters appear. These drugs do not cure the disease, but they can help relieve symptoms and shorten their duration.
If an eye or ear is involved, the appropriate specialist (ophthalmologist or otolaryngologist) should be consulted.
Wet compresses are soothing, but pain-relieving drugs are often required. Nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen may be tried, but oral opioid analgesics are often necessary (see Treatment of Pain).
To prevent bacterial infections from developing, people with shingles should keep the affected skin clean and dry and should not scratch the blisters.
Treatment of postherpetic neuralgia:
Mild pain requires no specific treatment other than nonprescription pain-relieving drugs (such as acetaminophen) or creams (such as capsaicin).
Although a number of treatments for severe postherpetic neuralgia have been tried, no treatment is routinely successful. Treatments may include
Last full review/revision December 2014 by Craig R. Pringle, BSc, PhD