Fungal Allergen Sensitization: Prevalence, Risk Factors and Geographic Variation in the United States

Many fungal species are associated with the pathogenesis of allergic disease, yet most epidemiologic studies on IgE-mediated fungal sensitization have only included a few species. To investigate fungal allergen sensitization prevalence, risk factors and geographic variation in the United States. From 2014-2019, 7,912,504 serum specific IgE (sIgE) test results for 17 fungal species were measured in 1,651,203 patients ages 0-85 years by a United States (US)-wide clinical laboratory. Fungal sensitization prevalence, patterns and relationship with demographic characteristics, clinical diagnoses and geographic regions were analyzed. 22.2% of patients were positive (sIgE>0.10 kUa/L) to at least one fungal allergen; 13.7% were positive >2 fungal allergens. Fungal species-specific positivity rates ranged from 7.4-18.6% and were highest to Candida albicans (18.6%), Alternaria alternata (16.6%), Stemphylium herbarum (14.9%), and Aspergillus fumigatus (14.2%). Other fungi that were frequently tested had relatively low positivity rates (e.g., Cladosporium herbarum 11.1%, Penicillium chrysogenum 10.7%). Independent risk factors for test positivity for all fungal species included male gender, teen ages (highest in ages 10-19 years), atopic dermatitis and asthma. Fungal sensitization was generally higher in urban areas and ecoregions composed predominantly of grasslands and prairies compared to those mostly composed of woodlands and forest, although there was greater variation in sensitization risk to different fungi in different ecoregions. Independent risk factors for fungal sensitization include male sex, teen ages, atopic dermatitis, asthma and ecological region. Fungal allergen sensitization is prevalent and current testing patterns in allergic disease evaluations may miss some sensitizing fungi. Fungal sensitization risk factors include asthma, atopic dermatitis, age, sex and geography.