Does chickenpox protect against skin condition?

Kids who get chickenpox may be less likely to develop atopic dermatitis and asthma when they're older than their peers who don't get chickenpox - including those that are vaccinated against it, suggests a new study.

But vaccine experts warn that the study was limited, and that one finding shouldn't challenge the benefits of the chickenpox vaccine.

"There's been a very visible health benefit in terms of use of the vaccine," Dr. Jane Seward, an expert on viruses at the Centers for Disease Control and Prevention (CDC), told Reuters Health. "We're seeing very, very significant declines in deaths and hospitalizations" from chickenpox, she said. "A single study with a single finding is interesting, but it needs ... more evidence."

Atopic dermatitis is a type of eczema, often causing itchy rashes, that arises from an allergic reaction. It may also be the "first step" in a series of allergies that leads to asthma, said the study's lead author, Dr. Jonathan Silverberg, from the State University of New York Downstate Medical Center in Brooklyn.

Previous research by Silverberg and his colleagues on the body's response to chickenpox and shingles, a related skin condition, suggested that getting chickenpox could decrease a child's risk of later developing atopic dermatitis. To test this hypothesis, they examined the medical records of almost 700 children and adolescents, some with atopic dermatitis and some without the bothersome skin condition.

For each subject, the authors looked back in the records to see if they had ever been infected with chickenpox.

Kids who had chickenpox - especially those who had it when they were young - were significantly less likely to get atopic dermatitis later, according to the results, which are published in the Journal of Allergy and Clinical Immunology. Among kids who eventually were diagnosed with atopic dermatitis, 20 percent had previously gotten chickenpox, compared with 28 percent of kids without atopic dermatitis.

The link went away for kids who had chickenpox when they were older than 10 - they were just as likely to get atopic dermatitis as other older kids who never had chickenpox.

Kids who had chickenpox were also less likely to be diagnosed with asthma after getting the virus.

Being vaccinated against chickenpox did not seem to give kids any protection against atopic dermatitis or asthma.

While "cost-effective" studies have shown that it makes economic sense to vaccinate kids against chickenpox, those studies haven't factored in the possibility that preventing kids from getting chickenpox might mean more will end up with atopic dermatitis or asthma, the authors say.

They argue that if further research confirms their findings, waiting to vaccinate kids against chickenpox until they are older (8 or 10 years old) could make the vaccine more cost-effective and prevent some cases of atopic dermatitis and asthma.