Specific Immunotherapy in Allergic Rhinitis

Specific immunotherapy has been widely used to treat allergic rhinitis. As with any other form of specific immunotherapy, careful patient selection is crucial. The diagnosis of allergic rhinitis needs to be secure, especially in those with perennial symptoms, and should be based on a careful clinical history supported by documentation of IgE-mediated sensitivity by allergy skin test or blood tests.

The efficacy of Specific immunotherapy in seasonal allergic rhinitis has been confirmed in a number of carefully controlled clinical studies involving pollens from grass, ragweed, birch, and mountain cedar. These studies have clearly demonstrated significant improvement in symptoms, allergies medication use, and quality of life and these changes are paralleled by a reduction in skin prick test reactivity, acute inflammatory reaction cell influx in the nasal inflamation mucosa and induction of Th1 response. Furthermore, it has been shown that the therapeutic benefit lasts for at least 3–6 years after completion of a 3 year course of treatment.

Although drug treatment for perennial rhinitis may be effective, the use of multiple topical or oral preparations throughout the year is inconvenient and treatment adherence is often poor. Also, in up to 30% of patients with perennial allergic rhinitis, the condition cannot be controlled by topical corticosteroid therapy. For these reasons mechanisms specific immunotherapy retains a place in treatment for perennial allergic rhinitis due to house dust mite or animals, although its effects have been less well studied than for seasonal pollenosis. Recent studies have also shown that house dust mite specific immunotherapy significantly reduced the development of sensitization to new, previously tolerated allergens in children. Formal evaluation is complicated by the heterogeneous and multifactorial nature of perennial rhinitis symptoms, in which non-allergic factors are frequently involved. The efficacy of specific immunotherapy in treating perennial rhinitis due to domestic pet allergy is more difficult to assess because of the intermittent and variable allergen exposure. Nevertheless, double-blind, placebo-controlled trials of cat dander SIT have shown that patients’ specific responsiveness to cat can be attenuated after only 3 months’ treatment, along with an elevated conjunctival provocation threshold, reduced skin test reaction to cat dander, reduction in bronchial sensitivity, and markedly reduced clinical response to field exposure to cats.

At present, the accepted indications for specific immunotherapy for the treatment of allergy rhinitis and perennial rhinitis vary between countries and largely reflect existing clinical practice. With the increasing costs of health care and the increasing sophistication of the healthcare market, questions of effectiveness and value for money are being asked more frequently. On the other hand, we are now more aware of the adverse effects of rhinitis on the quality of life. Thus the benefit, side-effects, cost, and duration of specific immunotherapy have to be balanced against those of symptomatic treatment. A significant proportion of rhinitis patients experience side-effects from their drug therapy (nose bleeds in up to 10% of those receiving nasal steroid sprays, and drowsiness in many who receive oral antihistamines) or may find the daily rigmarole of using their drugs unsatisfactory. A proportion of these ‘non-compliant’ patients may also profit from specific immunotherapy, but the risk/benefit and cost/benefit ratios need to be addressed on a case-by-case basis.