The type of sensitizing allergen can affect the evolution of respiratory allergy

Background: Numerous factors affect the evolution of respiratory allergy, in children, but little is known in adults. We assessed in a prospective study the influence of the type of allergen on the progression of disease. Methods: Outpatients, with respiratory allergy underwent skin tests and pulmonary function/methacholine challenge at baseline and after 3 years. Patients were subdivided in pure rhinitis or rhinitis + bronchial hyperreactivity (BHR). In polysensitized subjects a single relevant allergen (mites, grasses, birch, Parietaria) was identified based on symptom distribution and when needed on nasal challenge. Results: 6750 patients (age range 12-46) were studied. Of them, 17.8% were monosensitized but this percentage decreased to 10.4% after 3 years (P < 0.05). Subjects with pure rhinitis were 81% at the beginning and 48% at the end. After 3 years, the patients with bronchial responsiveness increased from 18% to 58% for mites, 22% to 49% for birch, 18% to 44% for grasses, 17% to 32% for Parietaria, with a significant difference among allergens (P < 0.05). Almost the same was seen in monosensitized subjects, being mites most likely to cause a worsening. All patients with BHR at baseline received immunotherapy. In these patients the onset of new sensitizations was significantly lower than in the group (pure rhinitis) receiving drugs only and lower airways symptoms disappeared more frequently. Conclusion: The different type of allergen influences the course of the disease, as well as the use of immunotherapy.