Allergic Diseases and Head and Neck Cancer: A Systematic Review and Meta-analysis

Allergic disorders such as asthma, atopic dermatitis, and allergic rhinitis affect a large portion of the global population. The relationship between allergies and cancer has been studied extensively, but results remain inconsistent for head and neck cancer. The aim of this meta-analysis is to evaluate whether there is a negative association between allergic disorders and head and neck cancer. A systematic search of five databases was conducted based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Cohort- and case-control studies examining allergies and head and neck cancer were included. Random-effect and fixed-effect models were used to calculate pooled relative risk, with heterogeneity assessed via the I2 and Cochrane's Q-test. Subgroup and sensitivity analyses were performed to explore variations by study design, allergy type, and cancer site. Twenty-five studies with 3.6 million participants were included. No significant overall association was found between allergic diseases and head and neck cancer (meta-RR: 0.89; 95% confidence intervals (CI): 0.76-1.05). Subgroup analyses revealed protective effects for asthma (meta-RR: 0.81; 95% CI: 0.70-0.95) and food allergies (meta-RR: 0.73; 95% CI: 0.54-0.99). Allergic rhinitis showed negative associations with oropharyngeal cancer (meta-RR: 0.76; 95% CI: 0.69-0.84) and hypopharyngeal cancer (meta-RR: 0.65; 95% CI: 0.55-0.78), but a positive association with nasopharyngeal cancer (meta-RR: 1.67; 95% CI: 1.15-2.43). These findings suggest complex relationships between allergies and head and neck cancer, with negative and positive associations varying by allergy type and cancer site. Further research is needed to clarify these associations.