Washington, November 12 : A new Cornell study suggests that allergy symptoms like sneezing, coughing, tearing, and itching may help prevent cancer.
Lead researcher Paul Sherman, a professor of neurobiology and behaviour, says that such symptoms may particularly prevent cancers of the colon, skin, bladder, mouth, throat, uterus and cervix, lung, and gastrointestinal tract.
He says that these cancers involve organs that "interface directly with the external environment".
His team examined 646 studies on allergies and cancers, which had been published over the past five decades.
Putting together "the most comprehensive database yet available", the researchers found "a strong relationship" between allergies and cancer in environmentally exposed tissues.
Sherman said that this relationship seldom exists between allergies and cancers of tissues that are not directly exposed to the environment, such as cancers of the breast and prostate, as well as myelocytic leukemia and myeloma.
His study also showed that allergies linked to tissues that are exposed to environmental factors - eczema, hives, hay fever, and animal and food allergies - were most strongly associated with lower rates of cancers in exposed tissues.
"One of our main results was that more than twice as many studies reported inverse allergy-cancer associations as reported positive associations," said Sherman.
Writing about the new findings in The Quarterly Review of Biology, he said that allergy symptoms might help protect against cancer by shedding foreign particles from the body.
He even noted that some of such particles might be carcinogenic or carry carcinogens.
"The idea is that the immunoglobulin E system (which is widespread among mammals) and its associated allergy symptoms serve a common prophylactic function, namely engulfing in mucous and rapidly expelling pathogens, natural venoms and toxins and other potentially carcinogen-carrying antigens before they can trigger neoplasia (the abnormal proliferation of cells)," Sherman said
Asthma is linked to higher rates of lung cancer, but this is one condition that reduces that the body's ability to expel mucus.
The researchers say that other allergies, which facilitate mucous expulsion, can lower the risk of lung cancer.
Sherman and his colleagues hypothesise that allergies may protect against certain types of cancer because they promote the expulsion of toxins and carcinogen-carrying antigens is also consistent with studies that find that people who express allergy symptoms are less likely to have toxic chemicals in their bodies.