Although immunotherapy initially was purely empirical, immunologic studies of treated patients in more recent years have shown several types of responses that might be beneficial to patients. Likewise, double-blind clinical trials have documented some clinical improvement if sufficiently large doses of certain allergens are administered to properly selected patients. The selection of patients for possible immunotherapy depends upon a large number of considerations, including the severity of their disease and response to simpler forms of treatment. More slowly absorbed allergen preparations may make immunotherapy less cumbersome and reduce risks. It is impressive that so many patients persist with such an inconvenient form of treatment. Perhaps this indicates that allergies are trivial only for those who don't have them.