Postherpetic neuralgia is a painful condition affecting your nerve fibers and skin. It's a complication of shingles, a second outbreak of the varicella-zoster virus, which initially causes chickenpox.

During an initial infection of chickenpox, some of the chickenpox virus can remain in your system, lying dormant inside nerve cells. Years later, factors such as age, illness, stress or medications can reactivate the virus. It can also reactivate for no apparent reason.

Once reactivated, the virus travels along nerve fibers, causing pain. When the virus reaches the skin, it produces a rash and blisters, known as shingles (herpes zoster). A case of shingles usually heals within a month. But some people continue to feel pain long after the rash and blisters heal. This pain is known as postherpetic neuralgia.

Treatment

Treatment for postherpetic neuralgia also depends on the type of pain you experience. Possible options include:

• Lidocaine skin patches. These are small, bandage-like patches that contain the topical, pain-relieving medication lidocaine. You apply the patches, available by prescription, directly to painful skin to deliver relief for four to 12 hours. Don't use patches containing lidocaine on your face.

• Antidepressants. These drugs affect key brain chemicals, including serotonin and norepinephrine, that play a role in both depression and how your body interprets pain. Doctors typically prescribe antidepressants for postherpetic neuralgia in smaller doses than they do for depression. Tricyclic antidepressants, including amitriptyline (Elavil), seem to work best for deep, aching pain. They don't eliminate the pain, but they may make it easier to tolerate. Other prescription antidepressants for postherpetic neuralgia include venlafaxine (Effexor), bupropion (Wellbutrin) and selective serotonin reuptake inhibitors such as sertraline (Zoloft), paroxetine (Paxil) and fluoxetine (Prozac, Sarafem).

• Certain anticonvulsants. Medications such as phenytoin (Dilantin, Phenytek), used to treat seizures, also can lessen the pain associated with postherpetic neuralgia. The medications stabilize abnormal electrical activity in your nervous system caused by injured nerves. Doctors often prescribe another anticonvulsant called carbamazepine (Carbatrol, Tegretol) for sharp, jabbing pain. Newer anticonvulsants, such as gabapentin (Neurontin) and lamotrigine (Lamictal), are generally tolerated better and can help control burning and pain.

• Painkillers. Some people may need prescription-strength pain medications, such as tramadol (Ultram) or fentanyl (Duragesic), to control their pain. However, these drugs are narcotics and can be addictive.

• Transcutaneous electrical nerve stimulation (TENS). This treatment involves the placement of electrodes over the painful area. The electrodes are then attached to a small, portable stimulator that you wear. The stimulator delivers tiny, painless electrical impulses that pass through the electrodes to nearby nerve pathways. You turn the TENS unit on and off as needed to control pain. Exactly how the impulses relieve pain is uncertain. One theory is that the impulses stimulate production of endorphins, your body's natural painkillers.

• Depression

In some cases, treatment of postherpetic neuralgia brings complete pain relief. But most people still experience some pain, and a few don't receive any relief. Although some people must live with postherpetic neuralgia the rest of their lives, most people can expect the condition to gradually disappear on its own within five years.