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("Allergy Shots")

Allergen immunotherapy (i.e. “allergy shots”) was first described as a treatment for allergies more than 100 years ago.


Since then, numerous high quality studies have shown that immunotherapy effectively treats: rhinitis, asthma, atopic dermatitis (eczema), and insect sting allergy.

In certain circumstances, studies suggest that immunotherapy may actually prevent the onset of new allergies or even asthma.


Allergen immunotherapy works by gradually exposing the patient's immune system to the allergen that is causing them symptoms. As their immune system is exposed to increasing doses, it changes in useful ways that make it less likely to react to the allergen in the future.


The exact mechanisms behind immunotherapy have been the subject of several studies performed over the last few decades that have clearly shown that useful changes in the immune system occur with this approach to treatment.

Immunotherapy is the only treatment available that actually changes the underlying immune problems that cause allergy. Most patients (up to 80%) will have a significant improvement with immunotherapy.

There are three main types of immunotherapy that your allergy specialist may offer you:

Sublingual Immunotherapy

Sublingual immunotherapy (SLIT) is the only allergen immunotherapy that is not injected. Instead, it is a once-a-day tablet that is placed under the tongue and dissolves within a few seconds. It is currently available for grass and ragweed allergy.

The therapy typically starts 2 to 4 months before the start of the pollen season and is taken daily until the end of the season.


SLIT is an effective way to reduce the symptoms of seasonal allergies.

One of the unique benefits of SLIT is that it can be taken at home and does not require visits to a physician's office after the first dose.

The drawback of SLIT is that, currently, it is only available to a limited number of allergens.

SLIT is generally safe and well-tolerated, but a small number of patients may have allergic reactions to the medication. The most common side effects are mouth itching or throat irritation, which usually improves with time.

More severe reactions are extremely rare. 

Talk with your allergists about the benefits and side effects of SLIT to decide if it is right for you.


Preseasonal Immunotherapy

Preseasonal immunotherapy involves a series of 4 to 9 weekly injections given prior to the start of the pollen season.

It is currently available for patients with allergy to trees, grass, and/or ragweed. 

The therapy typically starts 2 to 3 months before the start of the pollen season and is administered once weekly until the start of the season.

Preseasonal immunotherapy effectively reduces the symptoms of seasonal allergies. Patients are administered the shots each season for 5 consecutive seasons.

This provides both protection for the upcoming season and at the end of 5 years, they are protected from their allergies for future seasons. 

Although generally safe, there is a small risk of allergic reactions to the injections. Rarely, these reactions can lead to life-threatening anaphylaxis. As a precaution, patients are asked to wait 30 minutes after each injection.

Year-round (Perennial) Immunotherapy

Perennial immunotherapy is the classic form of immunotherapy and is available for most allergens that drive rhinitis and asthma, including non-pollens such as dust mites and pet dander.

As the name suggests, this form of immunotherapy is given year-round.

Patients start with a build-up phase where they receive injections once to twice a week. Following that, injections are administered once a month for five years. While most patients' symptoms improve after the first year, its effects become permanent (or at least long lasting) after the 5 years of treatment are complete.

Perennial immunotherapy is the best choice for patients who have multiple allergies, especially to non-pollens and who find first line treatments inadequate or difficult to tolerate.

As with preseasonal immunotherapy, the perennial injections are generally safe, but there is a small risk of allergic reactions that can lead to life-threatening anaphylaxis. As a precaution, patients are also asked to wait 30 minutes after each injection.

Your allergist will take a detailed history and help you decide if perennial immunotherapy is the best choice.


Illustrations used with permission. Provided courtesy of EBME inc.

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