BackgroundPractical issues dealing with the administration of allergen immunotherapy (AIT) by European and US allergists are not well known. Several concerns are only partially covered by guidelines. ObjectiveTo survey AIT practice patterns among worldwide members of the American Academy of Allergy, Asthma and Immunology (AAAAI). MethodsA web-based survey was conducted among AAAAI members on dosing, dose adjustment after missed doses, and duration of AIT. ResultsA total of 1,201 replies (24.7% response rate of which 10% of responses were from non-US and non-Canada members). A total of 57% to 65% of the US-Canadian dosing falls within the recommended Practice Parameter ranges (9.4%-19% too low). Dose adjustment after missed doses is based on time elapsed since the last administered dose by 77% of US-Canadian and 58% of non–US-Canadian allergists. Doses are reduced when a patient comes in more than 14 days for 5 weeks after the last administration and initial dosing restarted after more than 30 days for 12 weeks since last administration during the build-up or maintenance stage. After missing 1 to 3 doses, the dosing schedules were mostly followed (build-up phase: repeat last dose, reduce by 1 dose, reduce by 2doses; maintenance phase: reduce by 1 dose, reduce by 2 doses, reduce by 3 doses). AIT is prescribed for a median of 3 years by non–US-Canadian allergists but for a median of 5 years by 75% of US-Canadian allergists. Main reasons for continuing beyond 5 years were “after stopping, symptoms reappeared” or “patient afraid to relapse.” ConclusionMany patients receive less than recommended doses. Two areas in which to plan further research are establishment of an optimal dose-adjustment plan for missed applications and exploration of the maximum appropriate duration of immunotherapy.