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Antihistamine Use Tied to Brain Tumors

WebMD Health News
Reviewed by Louise Chang, MD

April 4, 2006 (Washington) -- Taking antihistamines may raise the risk of developing certain types of brain cancer, a new study shows.

"We want to stress that this is preliminary data and that antihistamines do not cause brain cancer," says researcher Michael Scheurer, PhD, of the University of Texas M.D. Anderson Center in Houston.

Given how many people take antihistamines to relieve sneezing, itching, dry mouth, and other allergy symptoms, "many more people would have brain tumors if they did," he tells WebMD.

Allergies Protect Against Deadly Brain Tumors

Reporting at the annual meeting of the American Association for Cancer Research, Scheurer says he believes this is the first study to look at the potential effects of antihistamines on the development of brain tumors in adults.

That said, a relationship between the two makes sense.

The reason: About a half dozen previous studies have suggested that people with allergies or asthma have a lower risk of the most deadly type of brain tumor, called glioblastoma.

"Allergies and asthma may produce enough inflammation in the brain to keep immune system cells active and working to prevent cancer," Scheurer says.

Since people take antihistamines to counter allergy's effects, the researchers wanted to see if the drugs also counter allergy's protective effects.

Gliobastomas are the most common of brain cancers, accounting for 50% to 60% of the 17,000 new brain cancers each year in the U.S. They're also the most potent, taking the lives of another 17,000 men and women, Scheurer says. "But very little is known about their cause."

Glioblastoma Risk Not Affected

Somewhat surprisingly, antihistamine use did not affect the risk of developing glioblastomas one way or another.

But the allergy drugs were associated with increased risk of other types of brain tumors. Specifically, people who used the medications regularly were 2.8 times more likely to develop lesser-grade anaplastic astrocytoma brain tumors and 86% more likely to develop low-grade glioma brain tumors than people who didn't take the drugs.

That's not to say the findings are trivial, however: Even low-risk brain tumors are often deadly, Scheurer says.

The study also confirmed that people with allergies or asthma are less likely to develop brain tumors. They were 36% less likely to have glioblastoma, 53% less likely to have anaplastic astrocytomas, and 37% less likely to have low-grade gliomas than people without the conditions.

Results also lined up with previous reports that both anti-inflammatory drugs and chickenpox confer protection against glioblastoma, Scheurer says.

"Once you have the chickenpox, the virus that causes it stays with you forever, lying dormant in the brain," he says. "It's hypothesized that the latent virus causes low levels of inflammation. And inflammation has been linked to the development of a variety of cancers."

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