Allergy Injections Immunotherapy

Allergy Injections Immunotherapy

In 1911 two ingenious pioneers in allergy research, L. Noon and J. Freeman discovered that hay fever victims injected with an extract of grass pollen before the grass pollen season began suffered fewer symptoms once the grass pollinated in the early months of the summer.

Modern research has documented the validity of these early studies. Allergy injections, also called immunotherapy, hyposensitization, or desensitization, are now a well-accepted form of treatment for many allergic conditions including hay fever (allergic rhinitis), insect allergy, and allergic asthma.

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In immunotherapy, a very dilute dose of the substance that the person is allergic to (the allergen) is injected into that person once or twice a week for three to four months. Each succeeding dose contains a higher concentration of the allergen.

• Weekly injections gradually build up to a maintenance dose, which is usually the highest dose the patient can tolerate without experiencing an allergic reaction. Once this top dose is reached, injections are given every three to four weeks and continued for at least three to five years on a year-round or perennial basis.
• The much older practice of giving injections for several weeks prior to a specific pollen season called preseasonal or coseasonal therapy, has given way to the more effective year-round perennial method. If allergy injections are deemed successful, they should be continued for three to five years.
• When it is clear that allergy injections are not helping or are causing adverse reactions, they should be discontinued. Patients who are relatively symptom-free for two consecutive years (or pollen seasons) deserve a trial vacation from shots. Some highly allergic patients may require more than five years of allergy injections.

How Do Allergy Injections Work

• The T cells also program the immune system to stop making allergic or IgE antibodies to the injected substance. Later on, when an allergen such as ragweed is inhaled, the pollen is confronted by the blocking antibody, which will then neutralize or block the allergen before it can get to the mast cells and trigger an allergic reaction.
• The net results of all this are a decreased level of IgE antibody and a decreased capacity to produce an allergic reaction. When allergy shots are successful, patients have fewer symptoms and require less medication.
• There are several reasons why some doctors question the value of immunotherapy in asthma. First, asthma is a very difficult disease to study. There are few well-designed double-blind studies dealing with asthma and allergy injections.
• In a double-blind study, some of the patients get an active drug (in this case, an injection with the actual allergen), while others receive a placebo or inactive drug. Neither the patient nor the doctor knows who is getting what until the study ends.
• Very few patients are willing to take the chance of receiving a saltwater placebo injection for several years. The second reason for the poor acceptance of allergy shots for asthma is that many patients with asthma do not have allergies.
• Many unscrupulous “shot doctors” fail to prescribe the correct medications or to implement the proper environmental controls before they subject their patients to years and years of worthless allergy injections.
• In my earlier teaching days, I knew that allergy shots were effective in treating asthma when administered to carefully selected patients, but at that time there was no concrete proof to present to skeptical medical students or house staff.
• Since then advances and discoveries in the field of immunology, combined with well-designed clinical studies, have conclusively shown that immunotherapy works in treating hay fever, stinging insect allergy, and allergic asthma.

Recent studies have demonstrated that immunotherapy with house dust mites, pollens, and cat allergen significantly lowers the overall reactivity of the asthmatic’s twitchy lung.

Who Needs Allergy Injections

I generally use the following guidelines to determine if allergy shots will help my asthmatic patients:

• Allergic or IgE-mediated asthma for more than two years
• Excess absences from school and work or repeated hospital visits
• Allergic asthma that is unresponsive to medications or environmental controls
• Inability to tolerate asthma medications
• Coexisting diseases such as allergic rhinitis or eczema
• Positive skin tests that correlate well with the clinical history

Risks Of Allergy Injections

Allergy injections are not entirely risk-free, and they should always be given under the supervision of a physician. After receiving your allergy injections, you should remain in the clinic or doctor’s office for thirty minutes, as most injection reactions occur within this time frame.

• Allergy injections should not be given at home by well-meaning relatives, neighborhood nurses, or other persons who lack experience in giving allergy shots or treating an allergic reaction caused by an allergy injection. The most common reaction is a local swelling at the site of the injection.
• The size and intensity of this local reaction will often determine the strength of the next dose. Sometimes patients experience what is called a systemic reaction in which they develop symptoms of an allergic reaction. Mild systemic reactions produce itching and sneezing, while more severe reactions may induce an attack of asthma.
• Most injection reactions promptly respond to an antihistamine, such as Benadryl, or an injection of adrenaline. Whenever a patient experiences a significant reaction to an allergy shot, the doctor should make a careful dosing adjustment prior to the next injection visit to prevent a recurrence of the injection reaction.
• Deaths from allergy injections (and testing) are reported, fortunately, they are extremely rare. Dr. Richard Lockey of the University of Florida has compiled data on forty-six fatalities associated with skin testing and allergy injections.
• These deaths, about one per year, took place between 1954 and 1985. Persons at risk included those experiencing seasonal flare-ups, patients taking beta-blocking drugs, and unstable asthmatics.
• Additional data gathered from studying severe injection reactions imply that those patients at greatest risk are unstable, severe asthmatics prone to rapidly deteriorating asthma whose pulmonary function tests (FEV1 and peak flow rates) are constantly below 70. percent of predicted.

Our practice has taken off allergy injections, for many patients with this profile, as our experience indicates that allergy shots usually do not work very well for this group.

Treatment Failures

The five most common causes are

1. Allergy “shot doctors” who treat people with nonallergic asthma
2. Poor control of the environment keeping animals in the home
3. Patients failing to keep appointments and follow a regular injection schedule
4. Patients developing new allergies not covered by the present injection program.
5. The physician’s inability to give an effective dose because of the patient’s severe sensitivity to the allergen

New allergy extracts under study appear promising. They will be more immunogenic (offer greater protection) and less allergenic (less likely to cause a reaction) These new extracts will require fewer injections to reach a top dose.

Many patients in the preliminary clinical trials have shown improvement after only two or three months of injections. The one drawback of these new medications is that they will be much more expensive than the present-day extracts.