Allergen Immunotherapy

A 10-year-old boy has received allergen immunotherapy for allergic rhinitis for approximately 6 months. Fifteen minutes after receiving his latest injections, the nurse checks his arm. She requests that you evaluate it because he has some redness and swelling that is about 2 inches in diameter at the injection site. He has no other symptoms.

Allergic rhinitis is treated by a variety of therapies. For mild-to-moderate symptoms, treatment with either oral antihistamines or topical therapy is extremely effective. The oral antihistamines are approved for children as young as 2 years of age. Some literature states that antileukotriene medications also are effective in allergic rhinitis. Topical therapies range from ipratropium bromide, which decreases secretions, to intranasal antihistamines and corticosteroids. Of these therapies, the intranasal corticosteroids are the most effective.

Allergen immunotherapy is the most efficacious therapy for patients who have severe allergic rhinitis. It has several advantages over other therapies. First, it is the only therapy that eventually can cure patients of their allergies; all other therapies only provide symptomatic relief. Monthly allergen immunotherapy also is administered less frequently than the other therapies once maintenance levels are achieved. The duration of allergen immunotherapy is usually 5 years. Choosing the appropriate patient for immunotherapy is extremely important and should be based on a combination of the patientís personal preference and the severity of disease. Many patients prefer monthly injections of immunotherapy to continuous topical or antihistamine therapy. Even once-daily administration can total approximately 800 doses a year of medication for a patient using oral and topical therapies. Also, many patients cannot tolerate topical or oral therapies due to sedation, lack of efficacy, or epistaxis.

Allergen immunotherapy does have some risk. Indeed, even fatalities have been reported in rare cases. The most severe reactions usually occur in patients who are very atopic as well as asthmatic. The American Academy of Asthma, Allergy, and Immunology recommends that all patients should receive allergen immunotherapy in a medical facility/office and be observed for 30 minutes after the injection for signs of anaphylaxis, including respiratory symptoms, lightheadedness, impending sense of doom, and urticaria. This time period was decided upon after a review of the literature that demonstrated that most patients had a reaction within 20 minutes of the allergen injection. It is also recommended that asthmatic patients be evaluated either by auscultation or peak-flow meter readings prior to receiving their injections. If they are symptomatic or have decreased pulmonary function, the immunotherapy should be delayed.

Adverse reactions to immunotherapy can range from local reactions, which are characterized by pain and swelling at the site of the injection, to anaphylaxis. Local swelling can, in fact, encompass several centimeters, such as described for the boy in the vignette. Such a reaction 15 minutes after the injection requires careful re-evaluation in another 15 minutes to determine whether systemic symptoms are present. If no systemic symptoms arise by 30 minutes after the injection, the next step is to adjust the dosage of medication. Some patients will have pain at the site of the injection, which can be relieved by adding an equal amount of saline to the injection and/or changing the contents of the immunotherapy injection. Even in patients who experience anaphylaxis following an injection, immunotherapy is not contraindicated if the risks are outweighed by the benefits. For patients who do have a severe reaction, the first-line therapy is subcutaneous epinephrine. A recommended course involves placing a tourniquet above the site of the injection and administering two full-dose injections of epinephrine: one at the site of the injection to decrease absorption of the allergen and the other in the opposite arm for treatment of the symptoms.
AAAI Board of Directors. American Academy of Allergy and Immunology. Guidelines to minimize the risk from systemic reactions caused by immunotherapy with allergenic extracts. J Allergy Clin Immunol. 1994;93:811-812
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