Background: Immunotherapy has been shown to reduce allergen sensitivity to allergens such as cat and dust mite. The aim of this study was to investigate the effect of cat or dust mite immunotherapy on bronchial hyperreactivity and the need for inhaled corticosteroids in children with asthma, cat or dust mite allergy, and hay fever.
Subjects: Twenty-nine children, 7 to 16 years old, completed the 3-year study. They were randomly allocated to receive cat/dust mite or placebo and birch/timothy immunotherapy.
Methods: Before immunotherapy was begun and then once each year, bronchial histamine challenges were performed. Bronchial allergen challenge with the perennial allergen was done before and after the 3-year study. Pharmacotherapy was given according to a standardized protocol.
Results: PC20 allergen increased significantly in both the active immunotherapy group (P <.001) and in the placebo-pollen group (P <.05). PC20 histamine increased continuously in the active immunotherapy group (P <.05 and P =.002 after 1 and 3 years, respectively) and had also increased after 3 years in the placebo-pollen group (P <.05). The difference between the 2 groups was significant for PC20 allergen (P =.001) but not for PC20 histamine. There was no significant change in the dose of inhaled budesonide needed for symptom control in either of the groups.
Conclusion: Pollen immunotherapy combined with inhaled corticosteroids results in improvement of both cat/dust mite bronchial sensitivity and hyperresponsiveness to histamine. The combination of cat or dust mite, pollen immunotherapy, and inhaled budesonide enhances this improvement. Cat immunotherapy also induces cat allergen tolerance.