Allergies to environmental inhalants such as pollens, molds, animals, dust mites, etc. are responsible for unpleasant and often debilitating symptoms in up to 30% of the American population. Known as hay fever, typical symptoms include nasal problems of stuffiness, congestion, runny nose, sneezing, itching, and eye problems of itching, tearing, redness. One of the most effective forms of treatment is allergy shots, or immunotherapy, since it can alter the course of the disease. Currently two types of immunotherapy are in use for inhalant allergies: injections (subcutaneous immunotherapy – SCIT), and drops under the tongue (sublingual immunotherapy – SLIT). This article is a review of a much larger report summarizing current practice in the US and Europe by the American and European Academies of Allergy reported this month in the Journal of Allergy and Clinical Immunology (see J Allergy Clin Immunol 2013;131:1288).
Patients develop allergy sensitivity to these common airborne agents because of a genetic susceptibility to make inappropriate immune reactions against them. Immunotherapy is designed to induce immune tolerance to these agents, thus changing this abnormal immune response to a more normal one. As immunotherapy proceeds, one sees a variety of changes in the abnormal allergy immune response leading to improvement in symptoms. For decades, SCIT has been the standard of care in the United States, but in the last decade studies have been emerging primarily from Europe showing the effectiveness of SLIT as well.
Adverse reactions may be local or involve the entire body ranging from mild to life-threatening anaphylaxis and even death. The frequency of serious reactions in patients receiving SCIT is 0.1% of injections, the majority occurring within 30 minutes necessitating giving them in a medical facility. Mainly in Europe, SLIT represents 80% or more of new immunotherapy treatments and has a better safety profile allowing it to be given at home. Side effects of SLIT include local mouth itching or mild swelling which improves as treatment progresses. No clear risk factors for serious reactions have been identified, but no deaths have been reported.
Because SCIT involves injections, the effective dose is 20 to 30 times less than the dose of SLIT. In the US, allergists will commonly include multiple allergens in dosing injections because people are typically sensitized to many agents, while SLIT therapy typically is used to treat single-allergen sensitization.
The duration of effectiveness of both SCIT and SLIT is 7-12 years after discontinuation. SCIT has a greater clinical benefit than antihistamines, leukotriene inhibitors (montelukast) and topical nasal steroids. Recent large scale studies suggest SLIT has much the same relative clinical effect as SCIT, and both appear to prevent development of new allergies and reduce the likelihood of developing asthma. Patients who receive either SCIT or SLIT experience as much as 80% higher cost savings than medications alone 3 years after completing therapy.
While immunotherapy is effective, not all patients benefit the same, adherence is difficult, studies looking at the effectiveness of SLIT in patients with multiple sensitivities are few, and oral treatment extracts are not yet approved in the US but will likely become available in the not distant future. Comparative studies looking at large populations of SCIT and SLIT treatment need to be conducted in this country where multiple allergens are used in treatment. At this time, indications to consider immunotherapy include long-standing symptoms, broad seasons, strong positive skin test responses, inadequate response to medications, complications, and diminishing quality of life.
-- article by Dr. Craig Moffat