There is no cure for most life-threatening allergies so, for the majority of severe allergy sufferers, avoidance of the specific allergens that trigger their reactions and being prepared to treat those that occur with an immediate shot of epinephrine are the only options.

Some people allergic to food, insect stings, or medications may outgrow or spontaneously become tolerant to their allergens.

For others, immunotherapy can offer a cure. For example, patients allergic to insect stings may attain long-term tolerance to insect venom through immunotherapy, a process during which carefully calibrated injections of venom are administered over a long period in order to change their immune systems, so that they no longer react to the insect venom protein.

While immunotherapy is an excellent way to protect against anaphylaxis for some allergies, it has side effects and may not be the treatment of choice for some patients with particular risk factors. In any case, safety precautions should be taken while undergoing immunotherapy.

Immunotherapy

Immunotherapy, or a regimen of "allergy shots," is a treatment designed to alter patients' immune system responses to substances they are allergic by exposing them to small amounts of the allergen and gradually increasing the exposure over a long period of time. Immunotherapy is the closest thing to a "cure" for non-life-threatening perennial and seasonal allergies (mold, pollen, dust mites, animal dander, or grasses) and asthma. It is not effective for most severe allergies that can produce anaphylaxis. One notable exception is for patients with insect sting allergies.

Patients who are given these calibrated injections over the course of several years can build a tolerance to the allergen. However, there is no guarantee that they will never react to the allergen again.¹

Administering Immunotherapy

An allergist or other physician who has been trained in the therapy administers immunotherapy by injecting a small, precisely calibrated amount of purified extract of the identified allergen under the skin of a patient's arm. Patients are then given injections of gradually increasing doses of the allergen at intervals that typically range from 1 to 8 weeks over the course of 3 to 5 years. The dosage, regimen intervals, and duration of therapy vary depending on the type and severity of the person's allergy.

Protecting Against Anaphylaxis

Unfortunately, for most people who are susceptible to anaphylaxis, immunotherapy is not a viable option. Immunotherapy has not been proven safe and effective for the treatment of food or latex allergies. Desensitization—a rapid course of increasing exposures to an allergenic medication—is available for patients with severe allergies to drugs that have no substitutes, but it is risky and may confer only temporary tolerance. However, regimens of immunotherapy shots for insect sting allergies or venom immunotherapy (VIT) have proved to be highly effective in providing long-term protection against further systemic reactions in 97% of cases treated.^2,3

Side Effects

Since immunotherapy involves exposure to an allergen, it can trigger allergic reactions with symptoms that range from localized irritation to potentially deadly anaphylaxis.

Localized reactions or mild anaphylaxis
These reactions include:

• Transient welts (also called hives or urticaria)
• Swelling at the injection site
• Sneezing
• Watery nasal discharge
• Itchy eyes

These reactions occur approximately once in every 200 to 500 injections.⁴

Systemic reactions or anaphylaxis
The symptoms of systemic reactions that may escalate to anaphylaxis include:

• Generalized hives
• Tightness of the chest
• Wheezing
• Throat swelling
• Loss of consciousness

Gastrointestinal symptoms, including cramping, bloating, gas, or diarrhea can also occur, but may not be immediately connected with exposure to an allergen.

Systemic allergic reactions occur in about 6% of patients who are treated with VIT, but there have been no reported deaths due to this procedure.⁵ During the past 40 years there have been at least 47 reported deaths due to immunotherapy injections for asthma and allergies to substances other than venom, most notably pollen.⁶ Given the millions of allergenic extract doses administered each year, the risk of death is very low. However, because it can happen, patients should be aware of the risk, as well as the steps that they can take to protect themselves.

Risk Groups

There is some risk of reaction from immunotherapy for all patients. Those who appear to be at the greatest risk for severe systemic reactions or anaphylaxis include patients who:

• Have unstable steroid-dependent asthma
• Have a high degree of allergic reactivity during diagnostic tests
• Have a history of systemic reactions to immunotherapy
• Experience asthmatic symptoms just before receiving an immunotherapy injection
• Are starting a new vial of extract, or who are given a rapid dose increase
• Are taking beta blockers or possibly those taking ACE inhibitors

Safety Precautions

Because severe systemic allergic reactions are a risk of immunotherapy, the American Academy of Allergy‚ Asthma & Immunology and the American College of Allergy‚ Asthma & Immunology stipulate the following:^7,8

• Physicians should evaluate the health of their patients before administering immunotherapy regimens. Patients should not be treated with immunotherapy while they are acutely ill, particularly if they are suffering an asthma attack or experiencing other respiratory difficulties.
• To avoid potentially dangerous interactions with medications, physicians should question their patients about any medications they may currently be taking.
• Only a physician specifically trained in immunotherapy, as well as in the recognition and treatment of anaphylaxis, should administer it (see Find an Allergist to locate a physician near you).
• Immunotherapy should be administered only in facilities that are equipped to treat anaphylaxis with epinephrine, that have emergency cardiopulmonary resuscitation equipment, and where injectable antihistamines, intravenous aminophylline, and intravenous corticosteroids are available.
• To maximize the chances of immediate medical attention should anaphylaxis occur, patients should remain under a physician's surveillance for at least 20 minutes after an immunotherapy injection. The time may be extended for high-risk patients.

References

1. Graft DF, et al. Position statement on the discontinuation of hymenoptera venom immunotherapy. AAAAI position statement #33. Available at: http://www.aaaai.org.
    
2. Hunt KJ, Valentine MD, Kagey-Sobotka A, et al. A controlled trial of immunotherapy in insect sting hypersensitivity. N Engl J Med. 1978;299:157-161.
    
3. Joint Task Force on Practice Parameters, American Academy of Allergy, Asthma and Immunology, American College of Allergy, Asthma & Immunology, and the Joint Council of Allergy, Asthma and Immunology. The diagnosis and management of anaphylaxis. J Allergy Clin Immunol. 1998;101(6 pt 2):S465-S528.
    
4. AAAAI. Immunotherapy. Tip #25. Available at: http://www.aaaai.org.
    
5. Valentine MD. Anaphylaxis and stinging insect hypersensitivity. JAMA. 1992;20:2830-2833.
    
6. Cook PR, Farias C. The safety of allergen immunotherapy: a literature review. Ear Nose Throat J. 1998;77(5):378-388.
    
7. ACAAI. Drugs and anaphylaxis committee of the American College of Allergy, Asthma and Immunology. Position statement on the administration of immunotherapy outside of the prescribing allergist facility. Available at: http://allergy.mcg.edu.
    
8. AAAAI. Guidelines to minimize the risk from systemic reactions caused by immunotherapy with allergenic extracts. AAAAI position statement #25. Available at: http://www.aaaai.org.