Does Allergy Protect Against Cancer?
Dr. Susan Waserman, MD, FRCP, Hamilton, Ontario
Over the years, we’ve sometimes heard that those with allergies are less likely to develop cancer, but we were not sure if this was a myth. We thank Dr. Susan Waserman for providing an opinion based on the research that has been done on this fascinating question.
What leads one person’s immune system to react to typically innocuous stimuli and another’s to overlook growth of aberrant cells is largely unknown. Asthma and cancer may reflect different programming of the immune system; the former a hyper reactive state, the later a type of immunodeficiency. Although the full complexity of the immune system is not entirely understood, the existence of different “programming” could suggest that certain individuals prone to one condition are at lower risk of developing another. In this case, allergy may protect against the development of cancer.
What is the evidence?
Although conflicting and limited, literature suggests that those with allergy have a reduced risk of developing cancer versus the general population1-8. There has been a general shift to better studies, including case-controls, multi-centered case-controls and rigorous meta-analyses, which provide stronger support for the relationship.
Wang et al performed a meta-analysis examining the link between atopic dermatitis (AD) and 6 types of cancer7. They found that history of AD decreased the risk of pancreatic, brain (glioma) and childhood leukemia (acute lymphocytic leukemia)7.
Grulich et al conducted a large (n=1398) population-based case-control study on adults 20-74 years-of-age examining birth order, atopy and the risk of non-Hodgkin’s lymphoma (NHL)2. In this study, AD did not significantly decrease the risk of NHL, but both hay fever and food allergy did2. The study is very specific, assessing the contribution of various atopic conditions (AD, hay fever, asthma, drug allergy, food allergy)2.
The mechanism of how allergy protects against cancer is unknown, however a couple theories have been proposed. Wang et al suggested that a TH2-bias represents a hyper reactive state of the immune system, which enhances immune surveillance, decreasing the proliferation of aberrant cells7. Likewise, Zacharia et al advocates a broader role of the T¬H2/IgE system, typically described as a system designed to destroy helminthes and parasites that spills over and causes allergy. Instead, the TH2 system may in fact serve to protect against a variety of environmental carcinogens and infectious diseases, minimizing biotic and abiotic hazards in the body. A highly active TH2 system would therefore reduce the risk of cancer by increasing the removal of carcinogens.
Although interesting, further work is required, using more precise definitions of “allergy” and examining the relationship between subtypes of atopic disease and cancer, since the protective mechanism may differ by both type and severity of both allergy and cancer.
- Cockcroft, D., Klein, G., Donevan, R. & Copland, G. Is there a negative correlation between malignancy and respiratory atopy? Ann Allergy 43, 345-7 (1979).
- Grulich, A. et al. Birth order, atopy, and risk of non-Hodgkin lymphoma. J Natl Cancer Inst 97, 587-94 (2005).
- LaVecchia, C., Negri, E., D'Avanzo, B., Boyle, P. & Franceschi, S. Medical history and primary liver cancer. Cancer Res 50, 6274-7 (1990).
- LaVecchia, C., D'Avanzo, B., Negri, E. & Franceschi, S. History of selected diseases and the risk of colorectal cancer. Eur J Cancer 27, 582-6 (1991).
- Mesquita, B.d., Maisonneuve, P., Moerman, C. & Walker, A. Aspects of medical history and exocrine carcinoma of the pancreas: a population-based case-control study in The Netherlands. In J Cancer 52, 17-23 (1992).
- Negri, E. et al. Allergy and other selected diseases and risk of colorectal cancer. Eur J Cancer 35, 1838-41 (1999).
- Wang, H. & Diepgen, T. Atopic dermatitis. British Journal of Dermatology 154, 205-210 (2005).
- Zacharia, B. & Sherman, P. Atopy, helminths, and cancer. Med Hypotheses 60, 1-5 (2003).
from Allergy & Asthma News, Issue 4 2006