November 5, 2008

Study Shows Allergies May Protect Against Cancer

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Sit in any lecture hall during the fall and spring months and you will inevitably hear someone cough or sneeze at least every five minutes. People plagued with allergies during these seasons see them simply as nuisances, but a study conducted by Cornell researchers revealed that allergies may actually help fight some cancers.
According to Profs. Paul and Janet Sherman, neurobiology and behavior, and co-authors of the study, the research was conducted by compiling all of the primary papers that they could find that related allergies to cancer. They found 148 publications that fit the criteria. They then grouped the results into three categories — one that showed a higher incidence of allergies was related to a lower incidence of cancer, one that showed the opposite, and one that showed that there was no relationship relative to controls.
Paul said, “One of the results found was that the frequencies of these relationships differed among different cancers with more than twice as many reporting inverse relationships as reporting positive associations.”
In the study, an inverse relationship was when a higher incidence of allergies correlated with a lower incidence of cancer, and a positive association was the opposite. The cancers that particularly had inverse relationships with allergies were cancers of the mouth, throat, colon, rectum, skin, uterus, cervix, lungs, bladder and gastrointestinal tract. The cancers that did not correlate with allergies were cancers of the ovaries, meninges, prostate and breast; also myeloma, Hodgkin’s disease, lymphocytic and myelocytic leukemia and non-Hodgkin’s lymphoma.
“The idea is that the tissues which allergies seem to protect from cancer are those that interface directly with the external environment,” Paul said.
According to Janet, this is because when antigens come into the body, the allergies combat them by removing them from the body through the allergic response. An external tissue receives antigens from the environment, and because of the allergic response, it can more swiftly expel the antigen back into the environment, which is not possible with the internal tissues. Examples of ways that allergic responses can expel antigens are through sneezing, coughing and diarrhea.
Paul specified that it is not the antigens themselves — such as pollen, dust and mold — that are necessarily the cancer causing agents. What is dangerous is what is riding on those particles — for instance, various environmental pollutants and toxins; essentially anything that could be carcinogenic.
“For example, plants sitting near the highway are a perfect sponge for the heavy metal toxins that come out of diesel fuels,” Janet said. “The pollen then releases into the air and, as humans, we breathe in the pollen but what we are actually gaining in addition to the regular pollen are the sulfur dioxides and other toxins that come from car exhaust.”
According to Paul, the study also found that asthma was the one allergy related to an external tissue that had a positive relationship with lung cancer. During an asthmatic attack, the airways constrict and it becomes hard to bring air in or mucous out. Therefore, the antigens come in but they cannot be expelled because the asthmatic attack holds them in, which actually increases the incidence of lung cancer.
“I think that this study is important because Darwinian medicine is a field that a lot of people don’t know about. The study takes a medical topic and says, well, we’re looking at these allergy symptoms and can come up with all sorts of medical explanations, but what about an evolutionary explanation,” Erica Holland ’05 said. Holland worked on the study when she was an undergraduate at Cornell, and helped with the manuscript after she graduated.
Paul said that the major implication of the study was that it suggested that allergies probably exist for a functional reason. He stressed that they were not qualified to give medical advice, but the study’s results implied that the severity of the allergies should be taken into consideration when seeking treatment. Many try to suppress allergies using things such as shots and Claritin. However, the study suggests that the benefits of the allergies may be worth the symptoms and should not be suppressed.
“We think that allergies are there to protect us against what is riding on pollen or cat fur or smoke,” Paul said. “I think it is now up to people who are the medical professionals to begin to try to address the question of how they should be treated.”
The study will be published in the December Quarterly Review of Biology.