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 patient’s 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.
References:
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
Druce HM. Allergic and nonallergic rhinitis. In: Middleton E Jr, Reed CE, Ellis
EF, Adkinson NF Jr, Yunginger JW, Busse WW, eds. Allergy: Principles and
Practice. 5th ed. St Louis, Mo: Mosby-Year Book, Inc; 1998:1005-1016
Nelson HS. Immunotherapy for inhalant allergens. In: Middleton E Jr, Reed CE,
Ellis EF, Adkinson NF Jr, Yunginger JW, Busse WW, eds. Allergy: Principles
and Practice. 5th ed. St Louis, Mo: Mosby-Year Book, Inc; 1998:1050-1062
Sly M. Allergic rhinitis. In: Behrman RE, Kliegman RM, Jenson HB, eds. Nelson
Textbook of Pediatrics. 16th ed. Philadelphia, Pa: WB Saunders Co;
2000:662-663