Specific allergen immunotherapy is the administration of increasing amounts of specific
allergens to which the patient has type I
immediate hypersensitivity. It is a disease modifying
therapy, indicated for the treatment of
allergic rhinitis, allergic
asthma, and hymenoptera
hypersensitivity. Specific
IgE antibodies for appropriate
allergens for
immunotherapy must be documented. Indications for allergen immunotherapy include (1) inadequate symptom control despite
pharmacotherapy and avoidance measures, (2) a desire to reduce the morbidity from
allergic rhinitis and/or
asthma or reduce the risk of
anaphylaxis from a future
insect sting, (3) when the patient experiences undesirable side effects from
pharmacotherapy, and (4) when avoidance is not possible. Furthermore, patients may seek to benefit from economic savings of allergen immunotherapy compared with
pharmacotherapy over time. Several studies have reported that
immunotherapy in children with
allergic rhinitis appears to prevent the development of new allergic sensitizations and/or new-onset
asthma. Humoral, cellular, and tissue level changes occur with allergen immunotherapy including large increases in antiallergen
IgG(4)
antibodies, a decrease in the postseasonal rise of antiallergen
IgE antibodies, reduced numbers of nasal mucosal mast cells and eosinophils, induction of Treg cells, and suppression of Th2 more than Th1 lymphocytes. There is a corresponding increase in
IL-10 and
transforming growth factor beta. In the United States, allergen immunotherapy is administered by the subcutaneous route in the physician's office, whereas primarily in some countries in Europe, it is administered for
allergic rhinitis and
asthma by the sublingual route by the patient at home.