ABSTRACT
I. INTRODUCTION Specific allergen immunotherapy (SIT) is a highly effective means of reducing sensitivity to specific allergens, and thereby reducing or abolishing the symptoms of allergic rhinoconjunctivitis and asthma. In most cases SIT is partially rather than fully effective, and patients continue to have some residual allergic symptoms, for which they may continue to take anti-allergic medication. SIT is often given to patients whose allergic conditions have not been well controlled with standard drug therapy, and it is common for these patients to continue their drug therapy during the course of SIT. Immunotherapy is thus combined with drug therapy in many patients. Separately, SIT carries a significant risk of side effects, largely but not exclusively due to allergic reactions to the vaccines. Some allergists have therefore tried to reduce the incidence of side effects by premedicating their patients with antihistamines before each SIT injection. Evidence from some research studies suggests that co-administration of SIT and drug therapy may modify the clinical response to SIT. This chapter reviews the evidence for this phenomenon and the possible mechanisms by which pharmacotherapy may diminish or increase the efficacy of SIT.
