Subcutaneous immunotherapy for the treatment of allergies

Subcutaneous immunotherapy (SCIT) was introduced a century ago. It represents for the third most important mainstay offered to allergic patients and is currently the only means of altering the abnormal immune response that underlies allergic disease. SCIT involves the gradual administration of increasing amounts of allergen to induce protective immunologic responses over a period of three to five years. The beneficial effects are usually seen within the first year of treatment. The mechanisms of action of SCIT are multiple and complex. The allergens that are known to be effective for use in SCIT include several tree, grass, and weed pollens, cat and dog dander, dust mites, certain molds, and cockroaches. The allergen used could be single or mixture of multiple allergens. There is no standard approach for the specific allergens or dose schedule to guide clinical practice. Although SCIT is used worldwide, sublingual immunotherapy (SLIT) has been conducted with single allergen extracts more recently. SLIT is considered a viable alternative to SCIT and is used in many areas of Europe, Latin America, and Asia. SLIT has not been approved by the U.S. Food and Drug Administration for use in the United States. The purpose of this report to review the evidence of comparative clinical effectiveness and safety profile of SCIT compared with antihistamine, SLIT or placebo in patients with allergy diseases and identify the existing guidelines on SCIT in the treatment of allergy diseases.