The Association between Allergy and Cancer: A Case-Control Study.

Background: Allergies may either have a protective or a promoting effect on cancers. This study seeks to explore the relationship between various types of allergies and three specific cancer types: lung, breast, and colorectal cancer, thereby adding fresh insights to the existing scientific.

Methods: Among the 556 patients, there were 115 cases of colorectal cancer, 305 cases of breast cancer, and 136 cases of lung cancer. The ratio of the case group to the control group was 1:1. We assessed the association between various variables, such as family history of allergy, allergies since the age of 10, pet allergies, seasonal flu, night and activity-related coughing, food allergies, itching or urticaria, childhood respiratory infections, and common colds, with the aforementioned cancers. The data were also analyzed using conditional logistic regression.

Results: The results showed a protective association between itching or urticaria due to environmental factors and colorectal cancer (adjusted odds ratio [AOR]: 0.4, 95% CI: 0.17-0.94), as well as lung cancer (AOR: 0.26, 95% CI: 0.09-0.75). Additionally, a borderline association was observed between itching or urticaria and breast cancer (AOR: 0.54, 95% CI: 0.28-1.03). Allergy to pets also exhibited an inverse borderline association with breast cancer (AOR: 0.44, 95% CI: 0.18-1.05) and lung cancer (AOR: 0.25, 95% CI: 0.06-1.14). Furthermore, night coughing and allergies since the age of 10 were found to increase the odds of developing breast cancer (AOR: 2.38, 95% CI: 1.44-3.92; AOR: 5.10, 95% CI: 2.56-10.56, respectively) and lung cancer (AOR: 2.40, 95% CI: 1.29-4.46; AOR: 8.71, 95% CI: 3.29-23.03, respectively).

Conclusion: allergies and cancer have a site-specific assciation . To confirm these findings and understand the reasons behind these associations, more investigation is required.