Allergy desensitization (or allergen immunotherapy) is a medical treatment that has the potential to reduce the impact of certain allergens, such as pollen, dust mites, dust, mould, animal dander, or insect venom. This is a particularly useful option for people with seasonal allergies (allergic rhinitis) who do not get sufficient relief from their usual medication.

Allergies: A widespread problem

Allergies occur when the immune system becomes abnormally sensitive and overreacts to substances that are generally harmless. In the case of allergic rhinitis, commonly known as seasonal allergy, the main culprits are pollens from trees/shrubs, grasses, or plants such as ragweed.

Each year, between 20% and 25% of Canadians experience allergy symptoms, which can vary in nature and severity. These symptoms include:

• Nasal discharge;
• Nasal congestion;
• Sneezing;
• A tingling sensation in the eyes or throat;
• Watery eyes;
• Coughing.

All too often, allergy symptoms impact daily activities and quality of life (insomnia, fatigue, lethargy, difficulty concentrating, etc.). They can also be accompanied by medical complications such as exacerbated asthma, sinusitis, or ear infections.

Fortunately, there are ways to help people with allergies cope with the discomfort.

Finding solutions

Generally speaking, allergy management involves three main components:

1. Reducing contact with allergens;
2. The use of medication to relieve symptoms;
3. Allergy desensitization (allergen immunotherapy)

Let's take a closer look at what this third option involves.

How does allergy desensitization work?

Allergy desensitization, or allergen immunotherapy, involves the repeated administration of gradually increasing doses of the allergen in question in order to help the body build up a tolerance to it. Over time, the immune system develops tolerance, which significantly reduces, and sometimes completely eliminates, allergy symptoms.

Unlike antihistamines and other medications, which provide temporary symptom relief, immunotherapy addresses the root cause of the problem. This is why it is considered the only treatment capable of permanently altering the course of an allergy.

There are two main types of treatment.

1. Sublingual immunotherapy (tablets or drops): A dissolving tablet is placed under the tongue once a day. The patient must then avoid swallowing for at least one minute and must not eat or drink for 5 minutes after taking the medication. The first tablet is taken under the supervision of an allergist, followed by a 30-minute observation period. After that, the treatment continues at home. The treatment for seasonal allergies begins 2 to 4 months before the pollen season and continues throughout the season. Treatment for dust mites is taken daily throughout the year.
2. Injection-based immunotherapy (subcutaneous route): The dose is gradually increased over 4 to 6 months, with at least one injection per week, after which injections are administered monthly. This is often the preferred approach when multiple allergies are involved. There is also a pre-season protocol, which involves a series of 4 to 11 injections before the pollen season begins.

Both methods are equally effective. However, the sublingual route has the advantage of carrying a lower risk of severe allergic reaction (anaphylaxis) can be administered at home after the first dose. However, injections can treat a wider range of allergens at the same time.

 

Which allergies can be treated with desensitization?

Allergen immunotherapy can be considered for several types of allergens:

• Pollen, which is the most common cause of seasonal allergies;
• Dust mites and dust, a common trigger of year-round allergies;
• Mould, which can cause persistent allergy symptoms, especially in damp environments;
• Animal dander (such as from cats and dogs), which is made up of tiny particles of skin, saliva, or urine that are dispersed in the air;
• Insect venom (such as from wasps or bees), which can cause severe allergic reactions, including anaphylaxis.

How long does allergy desensitization treatment last?

Desensitization is a long-term treatment. It generally takes 3 to 5 years of continuous treatment to achieve optimal and lasting results.

The benefits are noticeable from the first year onward and continue throughout the course of treatment. The benefits may even extend beyond the treatment period, provided the treatment was followed properly. Allergy symptoms may return over time, and in some cases, it may be necessary to resume immunotherapy treatment.

How effective is allergy desensitization?

The results of allergen immunotherapy are encouraging for several types of allergies.

• Pollen allergies: Approximately 80% to 85% of patients experience a significant improvement in their symptoms.
• Insect venom allergies: The effectiveness rate is around 98%.
• Allergies to dust mites, mould, and animals: Effectiveness is recognized, but may vary from case to case.

 

When should allergy desensitization be considered?

Allergen immunotherapy is particularly recommended for people who:

• have allergy symptoms confirmed by skin tests (prick tests) or blood tests;
• do not respond sufficiently to the usual medications (antihistamines or nasal corticosteroids);
• are experiencing unpleasant side effects from their current medication;
• have to take multiple medications to control their symptoms and want to reduce their use in the medium term;
• have had allergies for at least two seasons.

Contraindications

Allergy desensitization treatment is not suitable for everyone. It is generally contraindicated for people who:

• have severe or uncontrolled asthma;
• are immunocompromised or have cancer;
• are under 5 years old;
• are taking certain medications, including beta-blockers or certain treatments for high blood pressure.

If you are considering this treatment, an allergist will assess your situation to determine whether desensitization is appropriate for you.

At what age can allergy desensitization be started?

Treatment may be considered for both children aged 5 and older and adults, provided that the allergy diagnosis has been confirmed by an allergist. There is no specific upper age limit, but your doctor will take your overall health into account before recommending treatment.

Is desensitization dangerous?

As with any medical treatment, allergen immunotherapy carries certain risks, but these are generally well managed.

Common side effects (especially at the start of treatment):

• Itching or swelling of the mouth and lips (sublingual route);
• Irritation of the throat;
• itching in the eyes, nose, or throat;
• Headache;
• Nausea;
• Redness, swelling, or itching at the injection site (subcutaneous route).

These effects are usually mild and tend to decrease over the first few weeks of treatment.

 

Which doctor should I see for allergy desensitization?

Desensitization treatment must always be prescribed and initiated by an allergist, who is a specialist in the diagnosis and treatment of allergic diseases. The allergist will perform the necessary tests (skin tests, blood tests) to confirm the diagnosis and identify the allergens involved.

To schedule an allergy consultation, you can ask your family doctor for a referral. Your pharmacist can also guide you through the process and, under certain conditions, assess your symptoms and prescribe treatment to provide relief while you wait for your appointment.

Where can I get allergy desensitization treatment in Canada?

Desensitization treatment is initiated in an allergy clinic, a hospital setting, or an allergist's office. All injections are administered on-site. For the sublingual route, only the first dose is taken under medical supervision; treatment then continues at home, with regular follow-up with the allergist.

How much does allergy desensitization cost?

The cost of desensitization varies according to the type of treatment and the allergens being treated. In Quebec, consultations with an allergist in the public system are covered by the Régie de l'assurance maladie du Québec (RAMQ). However, the allergen extracts used in injections and sublingual tablets can vary in cost.

Prescription sublingual tablets are generally covered in part by drug insurance plans (the public RAMQ plan or private insurance). The monthly cost may vary, but it is often comparable to that of regular allergy medication.

The allergen extracts used for injections are prepared by the allergist; costs may vary from one clinic to another. It is recommended that you check your insurance coverage and discuss costs with your healthcare professional before starting treatment.

Your pharmacist can help you through your desensitization process

Allergy desensitization treatment requires discipline, supervision and ongoing medical monitoring. Your Jean Coutu–affiliated pharmacist can play a key role in the process in several ways:

• Advise you on managing your allergy symptoms and the treatment options available;
• Monitor your medication and checking for possible interactions with other medications;
• Provide you with information on the optimal and safe use of your sublingual tablets;
• Evaluate your symptoms and, depending on your condition, prescribe treatment to relieve them.

Feel free to make an appointment with your pharmacist to discuss your condition.