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 without fever. 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 four months after the shingles rash appeared 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 robert h. dworkin phd a professor in the department of anesthesiology at the university of rochester medical center in rochester n. y. but the longer you have phn -- especially after a year -- the less likely it is to resolve he says.
what are shingles and postherpetic neuralgia?