Immunotherapy for allergies has been around for over a century but it’s still relatively unknown. In this article we’ll look at different types of allergy immunotherapy, and at some important things to consider before embarking on a course of treatment.

Allergies, for example to pollen, dust mites, pet dander or insect stings, are caused by an overactive immune system. Your body treats an otherwise harmless substance as a threat and starts defending itself. This causes allergy symptoms that range from irritating but mild to so severe they’re potentially life-threatening.

When you have allergies the first step usually is trying to avoid the allergen triggering your symptoms. When you can’t, allergy medicines such as antihistamines and corticosteroids may help temporarily ease your stuffy or runny nose, sneezing and watery or itchy eyes.

Allergy immunotherapy goes further than temporarily relieving symptoms. It targets the underlying allergy, not your symptoms, and reprograms your immune system not to see the substance as a threat anymore. Immunotherapy for allergy is the only treatment that can change the course of the disease.

With allergy immunotherapy the goal is that your trigger isn’t a trigger anymore. It’s that simple. Many studies have shown people have fewer symptoms and need less allergy medication after immunotherapy for allergy.

You might already notice improvements in the first months of treatment but depending on the form of allergy immunotherapy it could also take 12 months. The experience after stopping allergy immunotherapy can vary too; symptoms return for some people while many find relief lasts for years. No more sneezing when you do meet pollen, dust mites or pet dander in ordinary everyday life, or not nearly as much.

Also, allergy immunotherapy may reduce the chances of getting new allergies. And it could help you avoid developing more serious symptoms.

Allergy immunotherapy could be for you if you’re dealing with symptoms such as a stuffy, runny nose and itchy, watery eyes caused by certain allergies and you have trouble keeping your allergies under control.

Some forms of allergy immunotherapy are suitable for children – but not usually for those younger than 5 years.

Allergy immunotherapy can reduce an allergic child’s symptoms and the need for allergy medication. It could also prevent them developing more allergies and progressing from milder to more severe symptoms or conditions. All this can make allergy immunotherapy valuable for controlling allergies in childhood.

Immunotherapy is available for allergies to for example:

• Tree pollen
• Grass pollen
• Weed pollen
• House dust mites
• Cats and dogs
• Bee and wasp stings

When you’re allergic to any of these substances, your immune system produces immunoglobulin E (IgE) antibodies specific to your triggers.

Before starting immunotherapy your health care provider or allergist will give you a skin prick test or an allergy blood test to look for these antibodies. That way they’ll be able to identify the allergens you react to.

Rather than avoiding the allergen, as you normally would, exposure is the treatment.

Allergy immunotherapy is made of the very substance you’re allergic to. It’s basically a standardized extract of certain pollen types, for example, or pet dander, even dust mites.

Small doses given regularly desensitize your immune system. Over time your body learns to tolerate the allergen instead of seeing it as a threat.

There are two types of allergy immunotherapy. Subcutaneous (SCIT) is the original method of injections just under the skin. These are often called allergy shots. The newest form of treatment is sublingual immunotherapy (SLIT), given as a fast-dissolving tablet under the tongue. Subcutaneous extracts and SLIT tablets are approved by Health Canada.

Your health care provider will regularly check the progress of the treatment and decide when it makes sense to stop injections. Usually, the full course lasts for three to five years.

The convenience of at-home treatment might be an advantage of allergy immunotherapy tablets (SLIT) – as well as avoiding injections.

There are five options approved by Health Canada so far: two types of tablets for grass allergies, one tablet for short ragweed, one for birch, alder and/or hazel tree allergies, and one for dust mite allergy.

A course of allergy immunotherapy tablets starts at the doctor’s office. The first time you’ll be monitored for any side effects. After that you can take your daily dose at home.

There will be regular check-ups and your health care provider will decide on the length of the treatment. It usually lasts about three to five years.

For example, scientists have discovered that immunotherapy for house dust mite allergy can help people who also react to pollen, reducing symptoms all year round, particularly during pollen season.

Allergy immunotherapy can also take advantage of cross-reactivity between allergens. This is when substances with a similar molecular structure to your trigger can give you a reaction. Basically, allergy immunotherapy may treat one allergen and at the same time reduce the symptoms caused by any cross-reactive allergens. For example, studies have shown that allergy immunotherapy with the pollen from one species of grass is effective in treating people sensitized to other related species.

All forms of immunotherapy can have side effects. These vary depending on the type of treatment. Local reactions aren’t serious and don’t need treatment. They also tend to happen at the start of allergy immunotherapy and less often after a couple of weeks. Try to think of it as a sign that allergy immunotherapy is working; after all, the point is to challenge your immune system. But always tell your health care provider.

There can also be systemic side effects, which means they impact on your whole body. We’ll explain about local and systemic side effects in detail below.

The most common side effects of subcutaneous allergy immunotherapy happen around where you have the injection. The skin might become red or swollen. Mostly this will clear up on its own. But antihistamine or corticosteroid cream may help calm the skin reactions in some cases.