Current Indications for Specific Immunotherapy

It is now almost a century since the pioneering work of Noon and Freeman was used to successfully treat hay fever symptoms using a low-dose incremental schedule of pollen injections. Noon based his doses of pollen extract on a pollen weight unit that remained in use for over 70 years; the basic principles of their work remain recognizable in the specific immunotherapy schedules used today.

During the 1920s and 1930s, interest in allergy developed rapidly, especially in the USA. Desensitizing injections, with varying dosage schedules, were administered to a wide range of patients and showed varying success rates. Gradually, it became clear that patient selection and proper attention to detail were vital in achieving successful desensitization; more recently, improvements to the preparation and standardized of allergen extracts have made the whole process more reliable and predictable.

In addition, our understanding of the immunologic basic of immunotherapy has dramatically increased. Our improving knowledge of immunoregulatory pathways is leading to novel approaches to immunotherapy which target more directly the determinants of allergen tolerance. In the near future, new ways of administering immunotherapy, either using different delivery systems or giving it together with other immunomodulating agents, will likely result in new and better immunotherapy regimens that lead to long-lasting allergen-specific tolerance and better clinical outcomes.

The main indications for SIT are in the treatment of patients who have experienced life-threatening allergic reactions to Hymenoptera stings, and those with allergic rhinitis due to pollen, dust mite and animal dander allergies. As per the current international guidelines, venom immunotherapy for Hymenoptera stings is not indicated for patients who have only had local reactions, but those with non-life- threatening systemic reactions should also be considered for allergen immunotherapy, taking into account the risk of future stings and underlying medical conditions before reaching a decision regarding suitability for SIT.

In patients with seasonal allergic rhinitis, SIT is currently offered to those with intractable symptoms that are either unresponsive or only partially responsive to conventional pharmacotherapy. A similar approach is taken for patients with perennial rhinitis that is predominantly driven by dust mite allergy. In those with troublesome reactions to animal dander, in particular where avoidance measures cannot be undertaken for occupational reasons, SIT is appropriate.

Although a number of studies have shown SIT to be efficacious in asthma (discussed below), the role of SIT in the current asthma management guidelines is unclear.