Allergy Immunotherapy: What Canadians Should Know (2025)

Allergy immunotherapy is a long-term treatment that helps your body stop overreacting to allergens by gradually retraining your immune system. Instead of simply masking symptoms with antihistamines, this approach works at the root cause — slowly building your tolerance to the substances that trigger allergic reactions. For many Canadians struggling with seasonal allergies, asthma, or insect sting reactions, it can deliver real, lasting relief.

How Does Allergy Immunotherapy Work?

Whether you are considering allergy shots in Canada or exploring sublingual immunotherapy options, understanding how the treatment works is an important first step. This guide explains who qualifies for allergy desensitization treatment, what the process involves from start to finish, potential risks and side effects, and what kind of results you can realistically expect.

What Is Allergy Immunotherapy?

Types of Allergy Immunotherapy Available to Canadians

Type	How It Works	Typical Duration	Best Suited For
Subcutaneous Immunotherapy (SCIT)	Allergen extracts injected under the skin in gradually increasing doses at an allergist’s clinic	3–5 years; build-up phase weekly for 6–12 months, then monthly maintenance	Allergic rhinitis, allergic asthma, insect venom allergies, pet dander
Sublingual Immunotherapy (SLIT) — Drops	Liquid allergen extract placed under the tongue daily at home	3–5 years of daily use	Pollen, dust mite, and mould allergies; patients unable to tolerate injections
Sublingual Immunotherapy (SLIT) — Tablets	Dissolvable tablets containing standardized allergen extracts taken under the tongue daily	Typically 3 years of continuous daily treatment	Grass pollen and ragweed allergies; Health Canada–approved options available
Venom Immunotherapy	Purified insect venom injected in escalating doses to reduce risk of anaphylaxis	3–5 years; some patients require lifelong maintenance	Individuals with confirmed severe reactions to bee, wasp, or yellow jacket stings
Rush/Cluster Immunotherapy	Accelerated build-up schedule with multiple injections per visit to reach maintenance dose faster	Build-up achieved in weeks rather than months; maintenance continues for 3–5 years	Patients needing rapid desensitization before allergy season or with limited clinic access

Allergy immunotherapy involves giving you a series of injections over a long period of time. Each injection contains a tiny amount of the allergen — the substance your body reacts to. Over time, your doctor gradually increases the dose. As a result, your immune system learns to tolerate the allergen instead of attacking it.

This process is called desensitisation. It does not just reduce your symptoms — it can actually stop allergic reactions from happening altogether. Think of it as retraining your immune system from the ground up. Learn more about how allergy shots work at Mayo Clinic.

When Is Allergy Immunotherapy Recommended?

Your family doctor or allergy specialist may recommend allergy immunotherapy if other treatments have not worked well enough. It is also a good option if your allergy medications cause serious side effects or interfere with other medicines you take. Some people also choose it because they want to reduce how many medications they take every day.

Conditions That Respond Well to Allergy Immunotherapy

Allergy immunotherapy works best for several common conditions. These include:

• Seasonal allergies: Pollen allergy is the most common type. If you dread spring or fall because of sneezing, itchy eyes, and a runny nose, this treatment may help significantly.
• Indoor allergens: Dust mites, cockroach particles, and pet dander can trigger symptoms all year long. Immunotherapy can help reduce your sensitivity to these triggers.
• Insect sting allergies: Reactions to bee or wasp stings can be life-threatening. Immunotherapy is highly effective for this type of allergy.
• Allergic asthma and eczema: Both are chronic conditions. Immunotherapy can reduce the frequency and severity of flare-ups over time.

However, allergy immunotherapy is not available for food allergies or chronic hives (urticaria). If you have these conditions, speak with your doctor about other treatment options.

Understanding the Risks

Most people go through allergy immunotherapy without any serious problems. That said, because the injections contain allergens, there is always some level of risk. It is important to understand what could happen so you feel prepared.

Local Reactions

The most common side effects are local reactions at the injection site. You may notice redness, swelling, or mild irritation. These reactions usually start within a few hours and go away on their own. They are considered normal and are not a reason to stop treatment.

Systemic Reactions

Less commonly, some people have systemic reactions that affect the whole body. These can include nasal congestion, sneezing, or hives. More serious symptoms may include throat swelling, chest tightness, or wheezing. If you experience any of these, tell the clinic staff immediately.

Anaphylaxis

Anaphylaxis is a rare but life-threatening allergic reaction. It can happen after an allergy shot, usually within the first 30 minutes. This is why you will always wait at the clinic after your injection — typically for at least 30 minutes — so medical staff can respond quickly if needed. Health Canada provides guidance on allergen immunotherapy safety standards.

Furthermore, your doctor may recommend taking an antihistamine shortly before each injection. This can help lower the risk of a reaction. Your doctor will decide if this is right for you.

How Long Does Treatment Take?

Allergy immunotherapy is not a quick fix. The full course of treatment usually takes three to five years. It is broken into two main phases.

Phase One: Build-Up Phase

The build-up phase lasts anywhere from three weeks to six months. During this time, you receive injections once or twice a week. Each dose contains a slightly higher amount of the allergen than the last. The goal is to gradually increase your tolerance.

Phase Two: Maintenance Phase

Once you reach your target dose, you move into the maintenance phase. Injections become less frequent — usually once a month. You stay in this phase for several years. Some patients notice improvement during the build-up phase, while others do not feel the full benefit until a year or more into treatment.

In addition, it is very important not to skip doses. Sticking to your scheduled injections helps reduce the risk of reactions and keeps the treatment working effectively.

Who Should Not Have Allergy Immunotherapy?

Most adults and children over age five can safely receive allergy immunotherapy. However, there are some situations where your doctor will advise against it or suggest waiting.

• Children with severe, uncontrolled asthma: Treatment is usually delayed until the asthma is better managed. Once the child’s breathing is more stable, immunotherapy may be started.
• Pregnant women starting treatment: If you are already in the later stages of immunotherapy and become pregnant, you can usually continue at your current dose. However, you should not start immunotherapy or increase your dose while pregnant.
• People taking beta-blockers: These medications can reduce how well epinephrine (adrenaline) works. Epinephrine is the main treatment for anaphylaxis. If a severe reaction occurs and epinephrine does not work properly, it can be life-threatening. Your doctor will carefully review all your medications before starting treatment.

How to Prepare for Allergy Immunotherapy

Before starting treatment, your doctor will run a series of tests to find out exactly what you are allergic to. These tests guide the preparation of your customised injections.

Allergy Skin Tests

Skin prick tests or intradermal tests involve placing small amounts of allergens just under the surface of your skin. After about 15 minutes, the doctor checks for redness or swelling. A reaction at a test site means you are allergic to that substance. Blood tests may also be done to confirm results.

During your immunotherapy programme, always tell the clinic staff if you are feeling unwell before an injection. Furthermore, keep track of any reactions you notice after each shot and report them to your doctor at your next visit. Good communication makes the treatment safer and more effective.

When to See a Doctor

If you think allergy immunotherapy might be right for you, start by talking to your family doctor. They can assess your allergy history, review your current medications, and refer you to an allergist if needed. If you do not have a family doctor, a walk-in clinic can help connect you with the right care. Most provincial health plans in Canada cover allergy testing and referrals to specialists.

You should also see a doctor right away — or call 911 — if you have a severe allergic reaction after any injection. Signs of anaphylaxis include difficulty breathing, throat swelling, a sudden drop in blood pressure, or loss of consciousness. Do not wait to seek help. Healthline offers a helpful overview of immunotherapy options for allergy sufferers.

Key Takeaways

• Allergy immunotherapy trains your immune system to tolerate allergens instead of reacting to them.
• It works best for seasonal allergies, indoor allergens, insect sting allergies, allergic asthma, and eczema.
• Treatment takes three to five years and includes a build-up phase and a maintenance phase.
• Most side effects are mild, but anaphylaxis is a rare risk — which is why you always wait 30 minutes at the clinic after each injection.
• It is not recommended for food allergies, pregnant women starting treatment, or people on certain medications like beta-blockers.
• Talk to your family doctor or visit a walk-in clinic to find out if allergy immunotherapy is right for you.
• Always consult a qualified healthcare provider before starting any new treatment. Your doctor knows your full medical history and can give you personalised advice.