context: Shingles, a viral infection of the nerve roots, affects 1 million people in the U. S each year. Most people recover from their bout, but for as many as 50% of those over age 60 who have not been treated, the pain doesn't go away. It can last for months, years, or even the rest of their lives. These people have what's called postherpetic neuralgia ( PHN), the result of the shingles virus damaging the nerves of the skin. In some cases, the pain is mild. In others, even the slightest touch -- from clothing or even a breeze -- can be excruciating. " PHN causes a great deal of suffering and high social costs," says Robert H. Dworkin, Ph D, a professor in the department of anesthesiology at the University of Rochester Medical Center in Rochester, N. Y. " It can severely disrupt people's lives." But the good news is that there are drugs that can help treat and even prevent PHN, and doctors are learning more about who is at greatest risk of developing this debilitating condition. Shingles is caused by the varicella-zoster virus, the virus that also causes chickenpox. In a person who has been exposed to chickenpox -- or its vaccine -- the virus never really goes away. It can lie dormant in the body's nerves. In most cases, it stays that way. But in some -- especially people with immune systems weakened by disease or treatment -- the virus can reappear. This is likely to happen years or decades after the person had chickenpox. When it comes back, the virus can cause shingles, a rash that often appears as a band on one side of the body. Early shingles symptoms can include: Headache Light sensitivity Flu-like symptoms Itching, tingling, or extreme pain where the rash is developing may come next, and the pain can be moderate to severe. Are you contagious? Though people who haven't had chickenpox can catch that condition from you, the shingles itself isn't contagious. For reasons that experts don't really understand, the pain of shingles lingers for some. If the pain lasts for at least 3 months after the shingles rash has healed, a person is diagnosed with PHN. In some people, the pain will subside. In others, it won't. " We don't have any idea why the pain goes away in some people and not others," says Dworkin. But the longer you have PHN -- especially after a year -- the less likely it is to resolve, he says. Researchers have long known that older people are more likely to get PHN, the nerve pain after shingles, but recent studies have found other factors that increase risks. In one study published in the journal Neurology, researchers -- including Dworkin -- looked at data from 965 people with shingles. The researchers identified five risk factors for developing PHN in people who had been recently diagnosed with shingles: Older Female Presence of symptoms before the rash appeared, like numbness, tingling, itching, or pain Severe pain during the illness's initial stages Severe rash Importantly, the researchers found the more risk factors you have, the greater the risk of developing PHN. For instance, 17% of women with shingles and 26% of those who had severe pain went on to get PHN. But 50% of women who were over age 60 and had symptoms before the rash, severe rash, and acute pain went on to get PHN. Researchers are not just looking at biological and neurological risk factors for PHN. Dworkin was also a co-author of a study looking at psychological risk factors, too. The results were published in the Journal of Pain in 2005. " It certainly looks like psychological stress can be a potent risk factor for PHN," Dworkin tells Web MD. The study showed that people with shingles who went on to develop PHN were more likely to have had symptoms of personality disorders, hypochondria, intense worry about their disease, and other bodily complaints. Dworkin says previous studies have already shown a connection between stress and shingles development. " One study even found that the risk of developing PHN was higher in people who were living alone when they developed shingles than people living with others," Dworkin says, perhaps indicating that social isolation increases the risks of PHN. But if you're worried about PHN, don't despair. There are medications that can cut your risks of getting the condition. There are three antiviral drugs used: famciclovir ( Famvir), valacyclovir ( Valtrex), and acyclovir ( Zovirax). These medications need to be started within two to three days of the onset of shingles. " If you look at the clinical trials with any of these drugs in people over 50," says Dworkin, "they cut the rate of pain at six months in half. That's a very significant improvement." They are also very safe and have few side effects, he says. But who needs the drugs? Dworkin says there's not a clear consensus yet. There are some obvious cases. " I think everyone would agree that someone who is over 50 and has severe symptoms should get preventative treatment," he tells Web MD. But for younger people or those with fewer risk factors, the course is less clear. " Some people think that everyone who gets shingles should get preventative treatment with antiviral medicines, because the medicines are so safe and have such few side effects," he says. Others argue that preventative treatment should only be given to those at greater risk. The main reason for this, Dworkin says, is cost. " A full course of treatment could cost anywhere between $100 and $160," he says. " That can add up, and insurance companies might not want to pay if the risks are very, very low." If you have shingles, it's important to talk to your doctor about your risk for developing PHN. Ask whether preventative treatment with antiviral drugs makes sense. If your doctor says it's not necessary, ask why. The full implications of the psychological risk factors for PHN aren't clear yet, says Dworkin. But he suggests that people with shingles should try to stay active and connected. " If psychological distress is a risk factor for PHN," he says, "then we think that people who have shingles might benefit from getting out and not being isolated and homebound." You might make an effort to stay connected to family and friends and not to dwell on your symptoms. Also, keep in mind that even if you do develop PHN, there are treatments that can help. " We have about a half dozen types of drugs that are used as first-line treatments for PHN," says Dworkin. They include lidocaine patch ( Lidoderm), pregabalin ( Lyrica), gabapentin ( Neurontin, Gralise, Horizant), capsaicin ( Qutenza, Zostrix cream), carbamazepine ( Tegretol), tricyclic antidepressants, and painkillers. The most important thing is to get prompt medical attention if you think you might have shingles. " If you have a one-sided rash -- especially if you're over 50 -- see your doctor right away," says Dworkin. " It could be shingles. And we know that prompt treatment can dramatically reduce the likelihood of developing long-term pain."