Allergic Rhinitis & Immunotherapy: Hope or Hype
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Allergic rhinitis (AR), one of the most familiar complaints seen in primary care, is a common immunologic condition that occurs in genetically predisposed patients. AR is routinely treated through allergen avoidance and pharmacologic therapy. When these measures fail, however, immunologic treatment may be indicated. This review of AR and its treatment focuses on injection and oral immunotherapy.
Types of AI
There are two categories of allergen desensitization therapy. The most common method is subcutaneous immunotherapy (SCIT), the so-called allergy shots. Less common and still somewhat controversial is sublingual immunotherapy (SLIT). Immunotherapy should be considered for patients who have secondary complications (eg, sinusitis, otitis) or asthma with allergies, or those in whom avoidance measures and medications fail. SCIT or SLIT may be desirable for patients with AR who have difficulty taking regular medications.
Subcutaneous immunotherapy. Currently, SCIT is the most recognized immunotherapy and the only one currently reimbursed by insurance. The procedure involves the subcutaneous injection of increasing doses of therapeutic solutions to which a patient has demonstrated sensitivity. The indications for this treatment are usually inhaled allergens, such as pollens and animal dander. SCIT may also be valuable in patients with asthma and atopic dermatitis.
The most common adverse reaction to allergy injections is a large localized reaction—primarily erythema, pruritus, discomfort, and possibly edema. Severe systemic reactions are extremely rare, with near-fatal to fatal reactions occurring at the rate of only 5.4 per million injections.11 The majority of these rare, albeit serious, complications are caused by higher-than-normal levels of pollen in the environment and dosing errors.11 Because of the uncommon but significant complications, patients undergoing immunotherapy should always receive injections in a medical office equipped with appropriate equipment and staff trained in handling anaphylaxis. It is standard protocol for patients to remain in the office for 30 minutes after administration for observation. Some clinicians prescribe epinephrine injectors (Epi-Pens) for patients to bring to every appointment as a condition for receiving their shot. Because of continuing controversy on this point, others only employ this requirement if the patient has a history of an adverse reaction.
Various protocols exist for the up-dosing of immunotherapy, most of which recommend weekly to twice-weekly injections prior to initiating maintenance therapy. Costs, risks, and benefits must be carefully considered and discussed with the patient prior to initiating immunotherapy.
Many insurance companies reimburse for immunotherapy, with varying copayments. Additionally, the time commitment may be taxing on the patient’s busy schedule. Weekly or biweekly appointments are required initially, and the patient must remain on site for half an hour. Although direct costs of SCIT are relatively easily measured and perhaps compensated, the indirect costs of time spent commuting and at the clinic are less tangible.
Success rates with SCIT may be more than 70% for certain allergens,18 but it is a long-term process with initial improvement often not seen until after six to 12 months of therapy. The benefits of therapy lead not only to reduction and suppression in symptoms (and medication), but also to reduction in comorbidity and lost school or workdays and improvement in quality of life.
Sublingual immunotherapy. Because of the possible safety concerns surrounding SCIT, along with problems relating to patient adherence to weekly office visits, alternative means of achieving allergen desensitization have been implemented. One of these methods, SLIT, has been increasingly supported by clinical evidence, especially in Europe. This therapy consists of applying aqueous allergen extract to the sublingual or oral mucosa, allowing it to be absorbed into the body. Subsequent swallowing of the extract allows the gut to respond with an increase in tolerance. The changes that result from this type of administration appear to be similar to those observed with SCIT.
SLIT has been in use for almost 30 years; the first published controlled study of this therapy was done in 1986 by Scadding and Brostoff.19 The World Allergy Organization recognized the safety and clinical efficacy of SLIT in 2009 after reviewing more than 60 controlled studies.20
A 2010 meta-analysis, reviewing documents from the prior 20 years of research, showed that SLIT decreased medication use and improved symptoms.21 Generally, SLIT was found to be more effective in adults than children. It was not as effective in patients with asthma as in those who were asthma-free. The timing of initiation of SLIT was also an important finding; when SLIT is used for grass pollen allergy, it should be started at least three months before the beginning of grass season.21 For other allergens, SLIT can be started at any time.
Because it is a home-based treatment, SLIT is far more convenient for the patient and therefore has become more popular in the US in the past decade. Its increased safety also contributes to its popularity. Although SLIT is commonly used in many parts of the world, at this writing, medications used in SLIT have not yet been approved by the US FDA. The FDA is currently reviewing two oral tablets for SLIT, and it is expected that its use in the US will increase once an approved product becomes available.22
It should be noted that no studies have directly compared SCIT and SLIT. Careful consultation between clinician and patient can help the patient arrive at the most appropriate modality for his or her condition based on symptomatology and lifestyle needs.
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