Indoor Allergen Sensitization to Cockroach and Its Relationship With Allergic Disease Outcomes in Young Adults From Singapore and Malaysia

Background Indoor allergen sensitization to cockroach (CR) is clinically relevant and exhibits substantial geographic heterogeneity. However, its relationship with pre‐existing atopy and allergic symptom burden in tropical urban environments remains uncertain considering the overwhelming influence of house dust mite (HDM) sensitization. This study aimed to characterize sensitization to the major indoor CR allergens— Periplaneta americana and Blattella germanica —and to evaluate its association with allergic disease prevalence, symptom severity, and exacerbation. Methods A total of 5350 young adults from the Singapore–Malaysia Cross‐sequential Genetics and Epidemiology Study (SMCGES) were assessed for sensitization to common indoor allergens, including HDM and CR, using skin prick testing. Associations between sensitization and clinical allergic outcomes were analyzed. In a sub‐cohort ( n = 736), serum specific IgE (SSIgE) profiling against 40 aeroallergens and seafood allergens was performed to assess co‐sensitization patterns. Results CR sensitization was identified in 23.1% of participants, with 19.7% sensitized to both HDM and CR. CR sensitization was associated with higher prevalence of asthma (OR 1.59; 95% CI 1.31–1.93), allergic rhinitis (AR; OR 1.42; 95% CI 1.22–1.65), atopic dermatitis (AD; OR 1.55; 95% CI 1.33–1.80), and atopic multimorbidity (OR 1.91; 95% CI 1.61–2.28). CR sensitization was also associated with higher frequencies of rhinitis symptoms, greater rhinitis symptom severity (OR 1.26; 95% CI 1.07–1.48), and higher total nasal symptom scores (OR 1.32; 95% CI 1.07–1.63). While HDM monosensitization was strongly associated with allergic outcomes, concurrent HDM and CR sensitization conferred additional risk and symptom burden. Polysensitized individuals also exhibited higher likelihood of developing CR‐specific IgE responses. Conclusion CR sensitization is prevalent in the tropical Singapore–Malaysia population and is strongly associated with polysensitization, higher allergic disease prevalence, and increased symptom burden. These findings emphasize the clinical significance of CR allergy and support targeted strategies for indoor allergen avoidance and environmental control.