Trends in hospitalizations for anaphylaxis, angioedema, and urticaria in Australia, 1993-1994 to 2004-2005

Background: Recent investigations in developed countries have found marked increases in the prevalence of allergic conditions. Objective: We sought to examine recent time trends in the prevalence of anaphylaxis, angioedema, and urticaria by describing trends and age and sex differentials in hospitalizations for these conditions in Australia. Methods: Data on hospital admissions and deaths for anaphylaxis, angioedema, and urticaria were extracted for the periods 1993-1994 to 2004-2005 and 1997-2004, respectively. For hospital admissions, age-standardized rates were calculated. Time trends and sex differences were quantified by using negative binomial models. Results: During the study period, there was a continuous increase in the rate of hospital admissions for angioedema (3.0% per year), urticaria (5.7% per year), and, most notably, anaphylaxis (8.8% per year). There was a particularly steep increase in the incidence of hospitalization for food-related anaphylaxis among children aged less than 5 years. Admissions for non-food-related anaphylaxis occurred predominantly in adults, particularly those more than 35 years of age. Among children, admission rates were higher in boys, but the sex difference was reversed among adults. Over an 8-year period, there were 106 deaths associated with anaphylaxis or angioedema. Conclusion: Hospitalization rates for allergic conditions are on the increase, but the nature and causative factors differ between adults and children. The relation of these changes to those in the prevalence of specific allergen sensitization in the community requires further investigation in population studies. Clinical implications: Among older persons, angioedema is becoming an increasing problem. Among children, hospitalization because of food-induced anaphylaxis is a growing concern.