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Allergies might fight off cancer: elevated immune response could target some tumors.

Hay fever, dog, peanut and other allergies may protect sufferers from certain types of brain tumors, a new study suggests.

In surveys of hospital patients, individuals with glioma--a form of brain and spinal cancer-were less likely than cancer-free individuals to report having allergies, researchers report in the February Cancer Epidemiology, Biomarkers & Prevention.

Epidemiologist Bridget McCarthy of the University of Illinois at Chicago and her team quizzed more than 1,000 hospital patients with or without cancer about their allergy histories. Of the 344 patients with high-grade glioma, about 35 percent reported having been diagnosed with one or more allergies in their lifetimes, compared with about 46 percent of the 612 cancer-free respondents. About 10 percent of patients with high-grade tumors had three or more types of allergies, as opposed to 19 percent of the controls. "The more allergies you have, the more protected you were," McCarthy says.

Glioma isn't the first cancer to be negatively correlated with common allergies, says Michael Scheurer, an epidemiologist at Baylor College of Medicine in Houston. Allergy-prone people may fight off colorectal and pancreatic cancer, and even childhood leukemia, better than sniffles-free people, according to some studies.

Just why these links exist isn't clear. Allergy sufferers mount heightened immune responses to certain foreign or dangerous cells and chemicals, says Scheurer. And cancer cells are certainly dangerous--human immune systems naturally seek the cells out. The immune systems in people with allergies may just do it better. "They have an overactive immune system, and maybe that's been protecting them from the development of tumors," he says.

In December, Scheurer and his colleagues reported finding a link between a higher risk for one type of glioma and use of antihistamine drugs such as diphenhydramine, Benadryl's active ingredient. The Illinois team did not find such a link.

Scheurer says Benadryl users shouldn't worry: "Brain tumors are very, very rare tumors, and a lot of people take antihistamines." He suspects that in a small set of individuals with a genetic predisposition to brain cancer, antihistamines may slow down the immune response, giving cancer cells an opening.

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Title Annotation:Body & Brain
Author:Strain, Daniel
Publication:Science News
Geographic Code:1USA
Date:Mar 12, 2011
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