BACKGROUND: Atopy is the familial or personal propensity to develop IgE antibodies against environmental allergens. Atopy, theoretically, could both prevent and promote the development of cancer. However, evidence from epidemiologic studies has been inconclusive.

OBJECTIVE: We investigated the longitudinal association between atopy and the incidence of total and specific types of cancers of 5 Danish population-based studies.

METHODS: Atopy was defined as serum specific IgE positivity against inhalant allergens. A total of 14,849 persons were followed up prospectively by linkage to the Danish Cancer Registry. We used Cox regression analysis, and risk was expressed as hazard ratios (HR) (95% CIs) for persons with atopy versus those without atopy.

RESULTS: There were 1919 incident cancers (median follow-up, 11.8 years). There were no statistically significant associations between atopy and risk of any cancer (HR 1.00 [95% CI, 0.89-1.12]), any cancer excluding nonmelanoma skin cancer (HR 0.93 [95% CI, 0.82-1.07]), head and neck cancer (HR 1.74 [95% CI, 0.98-3.09]), colorectal cancer (HR 0.92 [95% CI, 0.64-1.32]), cancer of the bronchus and lung (HR 0.78 [95% CI, 0.54-1.13]), breast cancer (HR 1.00 [95% CI, 0.73-1.37]), cancer of the uterus (HR 0.90 [95% CI, 0.43- 1.88]), prostate cancer (HR 0.79 [95% CI, 0.53-1.18]), urinary cancer (HR 1.08 [95% CI, 0.60-1.96]), malignant melanoma (HR 0.95 [95% CI, 0.54-1.66]), and nonmelanoma skin cancer (HR 1.20 [95% CI, 0.98-1.47]).

CONCLUSION: Our data did not support the hypothesis that atopy is associated with an altered risk of total cancer development, although effects of atopy on specific types of cancer cannot be excluded.