Background: As the global prevalence of allergy increases, it is clear that more individuals are presenting with complex and multiple allergies. The impact of various demographic and clinical risk factors on developing allergies has not been explored at a population level. Objectives: To ascertain if age, gender, ethnicity, UK geographical region of residence and being diagnosed with another allergy affect the risk of having allergies. Methods: A retrospective analysis was performed using cross-sectional data for the year 2018 extracted from the from the health improvement network (THIN) database. THIN is a live primary care database which holds entries about 6% of the UK population. A logistic regression analysis was carried out using demographic data and allergy diagnoses as independent variables. Results: Of the 3.03 million records analysed, 49.8% were male and 19.7% were children (aged < 18 yrs). There were gender, ethnicity and region-based differences in the prevalence of GP diagnosed allergic diseases in the UK. The odds of developing anaphylaxis are highest in individuals with food allergy [OR: 54.57 (95%CI: 45.65-65.22); p<0.001 for children and OR:18.05 (95% CI:16.79-19.41); p<0.001 for adults respectively]. Individuals with any diagnosed allergy had significantly higher odds of being diagnosed with others. Conclusions: Having an allergy significantly increases the odds of being diagnosed with others. There are age, gender, ethnicity and region based differences in the prevalence of allergies. These data suggest that the number of individuals with multiple allergies is increasing and that the needs of increasingly cosmopolitan populations should be taken into account when planning allergy services.

Background: Allergic rhinoconjunctivitis (ARC), asthma and eczema carry a substantial morbidity. These conditions often co-exist within the same individual and prevalence can differ based on age, ethnicity and gender. Objectives: Using a UK primary care database, we estimated the trends in prevalence over the last decade for ARC, asthma and eczema and associated risk factors. Methods: Longitudinal cohort analysis of the health improvement (THIN) database between 1 st Jan 2010 and 1 st Jan 2019. Logistic regression analysis was used to explore risk factors for diagnosis of these conditions. Results: An average of 4.17 million records per year were analysed, 19.4% were children and 49.75% were male. There was an increase in prevalence of ARC, asthma and eczema amongst adults during the study period, whereas ARC and asthma prevalence amongst children has fallen. By 2018, 1:8 adults and 1:14 children had ARC; asthma was diagnosed in 1:7 adults and 1:10 children whereas eczema was diagnosed in 1:6 adults and 1:4 children respectively. Ethnicity and gender modify the risk of being diagnosed with these conditions. Having other allergies substantially increases the odds of having asthma, eczema and ARC. Conclusion: The population burden of ARC, asthma and eczema in the UK is substantial. These conditions are often associated with other allergies and can, therefore, be complex to manage. These data support calls for improvement of pathways of care for allergy patients in the UK.