If I was exposed to someone with shingles, could this exposure activate my herpes simplex (cold sores)? Could my exposure also cause my 11-year-old son to get chickenpox for a second time?

B.M.

Chickenpox (varicella) and shingles are both caused by the same virus, the varicella-zoster virus. Herpes, both oral and genital, is caused by a different virus, the herpes simplex virus. These two viruses are related, but they really have nothing to do with each other as far as triggering shingles or cold sores.

Chickenpox usually occurs in children. As most people know, it first appears as a vesicular (blistering) rash on the trunk, and varies widely from a few vesicles to a rash that virtually covers the body. Recovery is uneventful in the vast majority of cases. People who have had chickenpox are almost completely immune against a second infection, so your son is at essentially no risk. However, the virus is never eliminated from the body, and about 10 percent of people will have a reactivation of their infection at some point, resulting in shingles. Unlike chickenpox, an outbreak of shingles, also known as herpes zoster, only involves a localized part of the body, such as the trunk or face. The vesicles themselves look very similar to those of chickenpox, but they are more painful than itchy. Shingles typically occurs in the elderly, though it can appear at any age.

Chickenpox, which is highly contagious, is spread from person to person via airborne droplets. More than 80 percent of people who are close contacts with a person with chickenpox become infected (assuming they hadn't previously been infected). It is also possible to develop chickenpox after exposure to someone with shingles, but this risk is much lower because people with shingles don't carry the virus in the respiratory tract.

If you have had chickenpox, your risk of becoming infected with the virus is negligible, and that means that your son is also not at risk, even if he had never had chickenpox himself. As I said above, cold sores are caused by the herpes simplex virus, and thus should not be affected by your exposure to shingles.