Postherpetic neuralgia (PHN) is a painful condition involving the sensory nerves of the skin. It is the most common complication of shingles, causing a burning and/or sharp pain that can last long after the blisters and rash of shingles disappear. More than 90% of patients with PHN present with allodynia, which is when pain is provoked by non-painful stimuli such as light touch. The pain is limited to the area of infection. Although the exact cause of PHN is unknown, it is generally believed to be produced by both the nerve inflammation and damage caused by the shingles virus.
The incidence of shingles infection increases with age and immune system impairment. Similarly, the rate of PHN development in people with shingles increases from 5% in those under 60 years old to 10% in those 60-69 years old, and to 20% in those over 69 years old. The major risk factors for PHN are older age, higher levels of pain during infection, and increased severity of rash.
A doctor can diagnose PHN when pain persists for longer than four months after the shingles rash resolves.
The pain of PHN may persist for months or even years. The treatment of PHN is difficult as, unfortunately, there is no one intervention that reliably manages the pain. There is a wide variety of medications available however, and it is common to try multiple options with your doctor before finding one that works. These include topical agents such as lidocaine or capsaicin patches, certain antidepressants such as duloxetine or venlafaxine, or specific anticonvulsants such as gabapentin and pregabalin.
In the case of PHN, the best treatment is prevention. Vaccination against shingles is recommended for all healthy adults over the age of 50, whether or not you have had shingles before.
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