Background: Some clinicians utilize allergen-specific immunotherapy (specific therapy), employing only the extracts of allergens that produce positive skin tests. Others use allergen-mixture immunotherapy (mixture therapy), employing premixed extracts containing both skin reactive and non-reactive (irrelevant) allergens.
Objective: The purpose of this study was to compare the efficacy of these two approaches and to identify sensitization to irrelevant allergens included in mixture therapy.
Method: A total of 20 adults with allergic rhinitis/asthma who were switched from successful specific therapy (average duration of 6.1 years) to mixture therapy (2.0 years) were evaluated with symptom-medication scores, skin test results, and local/systemic reactions at three time points: before specific therapy, before, and 2 years after mixture therapy.
Results: Symptom-medication scores for all patients improved at the end of specific therapy and remained improved during mixture therapy (12.3 versus 12.0 with P = .75). The sums of positive skin tests at three points were not different (7.8 versus 8.3 versus 9.8 with P > .4 at all points). Reaction rates did not differ either. Skin sensitization to irrelevant allergens occurred in five patients during mixture therapy. These patients, however, also experienced spontaneous conversions from negative to positive reactions to the allergens not included in the therapy, indicating that sensitization may be partly due to a spontaneous increase in skin reactivity.
Conclusion: These findings suggest that allergen-mixture immunotherapy is as efficacious as allergen-specific therapy and may be associated with skin sensitization in some patients. There was no evidence of increased adverse clinical reaction.