Shingles and Chickenpox (Varicella-Zoster Virus) - Complications

Itching. Many patients report itching as the primary symptom, rather than pain. In rare cases, it can be disabling (called postherpetic itch). Little research has been conducted on this complication, but in one study, it tended to occur in women and when shingles affected the head, face, and neck.

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Postherpetic Neuralgia (PHN). Postherpetic neuralgia (PHN) is pain that persists for longer than a month after the onset of herpes. It is the most common severe complication of shingles. It is not clear why PHN occurs. Some theories for its development are as follows:

The herpes zoster virus appears to produce persistent inflammation in the spinal cord that causes long-term damage, including nerve scarring.
Nerves that are injured in the initial attack may regrow abnormally and provoke an exaggerated response in the brain that signals intense sensitivity or pain.

Studies have reported a risk of PHN in people with herpes ranging from 10% to 70%. In general, however, the risk is likely to be in the lower range. The following are risk factors for PHN:

Age. PHN affects about 25% of herpes zoster patients over 60 years old. In addition, the older a person is the longer PHN is likely to last. It rarely occurs in people under age 50.
Gender. Some studies have suggested that women may be at slightly higher risk for PHN than men, although a 2000 study found no difference.
Having Severe or Complicated Shingles. People who had prodromal symptoms or a severe attack (numerous blisters and severe pain) during the initial shingles episode are also at high risk for PHN. The rate is also higher in people whose eyes have been affected by zoster.
Immune Factors. People with impaired immune systems do not seem to be at any higher risk for persistent PHN than those with normal immune systems.

In most cases, PHN resolves within three months. In fact, some experts define persistent pain after a herpes zoster attack as subacute herpetic neuralgia if it lasts between one and three months and as PHN only if it lasts beyond three months. According to studies in 2003 report, only about 10% of patients experience pain after a year. Furthermore, one study suggested that severe and very persistent PHN is not common. Unfortunately, when PHN is severe and treatments have not been very effective, the persistent pain and abnormal sensations can be profoundly frustrating and depressing for these patients.

Secondary Infection in the Blisters. If the blistered area is not kept clean and free from irritation, it may become infected with Streptococcus A or Staphylococcus bacteria. If the infection is severe, scarring can occur.