Allergen-specific immunotherapy for allergy treatment (perhaps better known as “allergy shots”), is a medicinal plan that works by “training” the immune system to stop overreacting to allergens. This essentially presents the problematic substance to the immune system often enough, and in small enough quantities, to breed familiarity. This process, also called “desensitization,” is based on the observation that sometimes the immune system can “learn” to at least tone down—if not ignore—its response to allergens.

This type of treatment, usually performed under the care of an allergy and immunology specialist, begins by identifying the specific allergens to which the patient reacts. Candidates include people with seasonal allergies, perennial allergies, and insect venom allergies. Some patients who are allergic to insect venom—such as a bee sting—may require immunotherapy to reduce the risk of a serious, life-threatening reaction. There are no allergy shots for food allergies. 

How to Determine the Allergies

There are two methods used to identify a patient’s specific allergy triggers. The first involves pricking the skin of the back or arms with diluted solutions containing various known, common allergenic proteins, such as tree pollens, molds, dust mites, and others. The patient’s skin is observed for a time and evaluated for any visible reaction, such as redness and swelling. The clinician measures the size and other characteristics of any bumps that arise, gathering information about the patient’s immune response to particular allergens. A second method involves drawing blood and directly assessing circulating antibodies to specific allergens in the blood.

Starting Immunotherapy

After determining which allergens a patient is allergic to and how serious the reaction is likely to be, the clinician concocts an extremely diluted solution containing minute amounts of the offending allergen or allergens. Small amounts of this solution are then injected beneath the outermost layers of skin, usually on the arm, and the patient is monitored for minimally 30 minutes to ensure that they won’t suffer an adverse reaction.

In some instances, swelling or redness may develop at the site of the injection. Less often, a patient might develop a systemic reaction. This might involve hives, tightness of the chest, or wheezing. At its most severe, an allergic reaction can lead to a condition called anaphylactic shock. This may involve serious constriction of the airways that leads to suffocation, and must be countered with an injection of adrenaline.

After the clinician is satisfied that the patient won’t react to the injection in this manner, the patient is dismissed until the next scheduled injection. Over time, the amounts of allergens are gradually increased with the hope that the patient’s immune system will eventually build up a tolerance to them, essentially “learning” that the allergens don’t represent an actual threat and therefore don’t warrant a strong immune response.  

Initially, shots are usually given one to three times per week, for as long as three to six months. After this “build up” phase, during which the amounts of the allergen are gradually increased, a maintenance phase begins. During maintenance, which may last for five years or more, the patient receives a maintenance dose about once a month.

Subcutaneous Versus Sublingual

Allergy desensitization therapy using injections under the skin has been around for nearly 100 years. A newer, potentially less risky therapy not yet approved by the U.S. Food and Drug Administration for use in the United States, uses an allergen placed under the tongue. This delivery method, known in medical terms as sublingual immunotherapy, is an alternative to injections given beneath the skin (subcutaneous immunotherapy). It’s gradually gaining in popularity, at least in Europe and elsewhere around the world. It may be somewhat less likely to cause systemic reactions than subcutaneous immunotherapy; but the jury is still out, at least in the United States.

Does It Work?

Regardless of how it’s done, does allergen-specific immunotherapy work? The answer is: yes. Almost always, actually.  According to the American College of Allergy, Asthma, and Immunology, the therapy is “highly effective” against allergic rhinitis and may help prevent allergy-induced asthma as well. It’s the only treatment that addresses the underlying cause of allergies, rather than addressing symptoms.