If allergy season has you sneezing, wheezing or itching, is your risk of developing a deadly form of brain cancer less?

No one can say for sure, but researchers found an inverse association between allergies, asthma and eczema and a brain cancer called glioma, meaning that people who have the allergic conditions may be less likely to develop the brain cancer, said an international consortium of researchers from 14 centers led by researchers from the Dan L Duncan Comprehensive Cancer Center at Baylor College of Medicine. A report on their work appears online in the Cancer Epidemiology, Biomarkers & Prevention journal, published by the American Association of Cancer Research.

Dr. Melissa Bondy, associate director for cancer prevention and population science at the Duncan Cancer Center, said the most recent study – the largest known of the subject – adds weight to the scientific literature on the inverse association and means that researchers now need to determine the mode of action or how allergies, asthma or eczema could be protective.

“Many other studies have shown this relationship,” said Bondy, also a McNair Scholar. “We sought to verify this relationship in the largest study to date so that we could provide a scientific consensus statement on the topic. We feel it’s now time for the next steps to be taken in this research area.”

In an analysis comparing the health data of 4,533 patients who had glioma to 4,171 people recruited from a population without brain cancer, the researchers found that a history of asthma, respiratory allergies and eczema, an allergic skin condition, was associated with a reduced risk for glioma or brain cancer, validating many previous studies that have reported similar findings.

In the study, researchers asked subjects and controls about their past medical history and what they had been exposed to in their jobs. They were also asked about whether they had allergies, asthma and eczema in different time periods of their lives.

Overall, having respiratory allergies was associated with about a 30 percent lower risk of developing a glioma compared to not having respiratory allergies, the researchers found. The association remained the same when the patients were restricted to higher grade gliomas but was not statistically significant in people who had lower grade tumors. The same was seen with eczema.

In the report, the authors wrote, “Based on the growing body of evidence in the literature, the scientific community may be approaching a consensus on the role of allergies in glioma risk.”

The study confirms the need for biologists and immunologists to dig deeper into understanding the mechanisms for the relationship, said Bondy, corresponding author of the report.

Dr. E. Susan Amirian, assistant professor in the Duncan Cancer Center and an assistant professor of pediatrics – hematology and oncology at Baylor, was first author on the study. Of note was the fact that the reduced risk was shown in glioblastoma patients, who have the highest grade form of brain cancer, Amirian and Bondy said.

A clearer understanding of why this happens is of great interest to the brain cancer community, they said.

Co-authors on the report included Renke Zhou, Michael E. Scheurer, Georgina N. Armstrong, Ching C. Lau, all of Baylor; Margaret R. Wrensch, Lucie S. McCoy of the University of California in San Francisco; Sara H. Olson and Jonine L. Bernstein of Memorial Sloan-Kettering Cancer Center in New York, New York; Dora Il'yasova of the Georgia State University School of Public Health; Daniel Lachance and Robert B. Jenkins of the Mayo Clinic in Rochester, Minn.; Elizabeth B. Claus of Yale University School of Medicine in New Haven, Conn.; Jill S. Barnholtz-Sloan of the Case Western Reserve University School of Medicine in Cleveland, Ohio; Joellen Schildkraut and Francis Ali-Osman of the Duke University Medical Center in Durham, N.C.; Siegal Sadetzki of the Tel Aviv University in Israel;  Christoffer Johansen of the University of Copenhagen in Denmark;  Richard S. Houlston of the Institute of Cancer Research, Sutton, Surrey, United Kingdom; Ryan T. Merrell of the NorthShore University HealthSystem in Evanston, Illinois; Faith G. Davis of the University of Alberta in Canada; Rose Lai of the University of Southern California Keck School of Medicine, Los Angeles; Sanjay Shete of The University of Texas MD Anderson Cancer Center; Christopher I. Amos of The Geisel School of Medicine at Dartmouth, Hanover, New Hampshire and Beatrice S. Melin of Umeå University, Umeå, Sweden.

Funding for this study was provided by National Institutes of Health (R01CA139020 (M.L. Bondy) and R01CA52689 (M.R. Wrensch), The McNair Medical Institute and the Population Sciences Biorepository at Baylor College of Medicine (P30CA125123, M.E. Scheurer).