A number of specialized databases have been developed to facilitate studies of human allergens. These include molecular databases focused on protein sequences and structures, informational databases focused on clinical, biochemical and epidemiological data related to protein allergens, a database on allergen nomenclature, and other knowledge bases or informational websites that are peripherally-related to research on allergens. Examples of each type of databases are listed and described briefly in this review. Database construction and maintenance and their impact on database quality and usefulness are also discussed.