Immunotherapy is a generalised term for treatment that uses the immune system to fight disease or infection. The main two immunotherapies are for cancer and allergies. Cancer immunotherapy is also called ‘targeted treatment’ or ‘biological therapy’. Allergies are a type of immune system dysfunction, where the body incorrectly identifies and attacks normal everyday proteins like pollen, dust or food, causing lots of unnecessary symptoms. In simple allergy terms this type of immunotherapy is used to retrain the immune system to correctly identify these proteins and reduce or eliminate allergy symptoms. It is often also called desensitisation.

How does immunotherapy reduce allergic reactions?

Immunotherapy works by exposing the patient to very small doses of the allergen (the substance that causes the allergic reaction) at regular intervals, either by injection (shots), drops or tablets under the tongue and then working up to larger and larger doses. This helps the immune system to tolerate the allergen and not react to it so strongly. Immunotherapy for allergies is usually reserved for patients with severe or persistent allergies that do not respond well to other treatments.

What are the different types of immunotherapy for allergies?

There are different types of immunotherapy for allergies, depending on the route of administration and the type of allergen. The main types of immunotherapy for allergies are:

Subcutaneous immunotherapy (SCIT) - This is the most common and most effective type of immunotherapy for allergies. It involves giving gradually increasing doses of the allergen by injection (shots) under the skin (subcutaneous), usually in the upper arm. The injections are given at regular intervals, ranging from weekly to monthly, depending on the phase of treatment. The treatment can last from three to five years or longer. SCIT can treat a wide range of allergic conditions, such as hay fever, asthma, pet allergy and some food allergies. SCIT can also prevent the development of new allergies or asthma in some cases. Venom Immunotherapy (VIT) is a sub-category of SCIT and is a treatment to reduce the risk of severe allergic reactions to bee and wasp stings.

Sublingual immunotherapy (SLIT) - This is an alternative treatment without injections. It involves placing a tablet or a drop containing the allergen under the tongue, where it dissolves and is absorbed by the mucous membranes. The doses are given daily at home, after an initial supervision by a doctor or an allergist. The treatment can last from one to three years or longer. SLIT can treat some allergic conditions, such as hay fever, asthma, and some pet allergies. In the US SLIT is currently approved by the FDA for grass and ragweed pollen allergies and dust mite allergy.

Epicutaneous immunotherapy (EPIT) - This is a newer immunotherapy, it involves applying a patch containing the allergen on the skin, usually on the back or the arm. The patch is worn for a few hours a day and replaced every day or every other day. The treatment can last from six months to a year or longer, depending on the patient’s response and goals. EPIT has so far been recommended in the treatment of certain food allergies, such as peanut allergy. EPIT is not yet approved by the FDA, but it is being studied in clinical trials.

Oral immunotherapy (OIT) - This is another newer way to treat food allergies. It involves giving gradually increasing doses of the food allergen by mouth, usually in a capsule or a liquid form. The doses are given at regular intervals, ranging from daily to weekly, depending on the phase of treatment. The treatment can last from several months to a year or longer, depending on the patient’s response and goals. OIT can treat some food allergies, such as peanut allergy, milk allergy, egg allergy, and wheat allergy. OIT is not yet approved by the FDA, but it is being offered by some doctors or allergists under special protocols.

Each type of immunotherapy for allergies has its own benefits and risks, and it may not work for everyone. You should talk to your doctor or allergist before starting any type of immunotherapy for allergies.

In the UK, SCIT and SLIT are both authorised on the NHS for venom immunotherapy, for hayfever (allergic rhinitis) and for allergic asthma caused by dust mites. The British Society for Allergy and Clinical Immunology currently (2023) recommend OIT for peanut allergy. Immunotherapy for other food allergies are frequently offered at private allergy clinics.

What are the benefits of immunotherapy?

The benefits of immunotherapy depend on the type and purpose of the treatment, but generally speaking, immunotherapy can help your body fight disease or infection more effectively. Some of the benefits of immunotherapy are

Immunotherapy may work when other treatments don’t. Some allergies don’t respond well to conventional treatments like medication but may improve after immunotherapy.

Immunotherapy causes fewer side effects than medications. Immunotherapy is more specific and selective than other treatments, meaning it targets only your immune system and not all the cells in your body. This reduces the risk of unwanted side effects from allergy medications.

Immunotherapy may prevent the recurrence or symptoms. Immunotherapy can train your immune system to remember that allergenic proteins are not foreign bodies to be attacked. This is called immunological memory, and it can help you stay healthy for a longer time and avoid relapses or complications.

What are the risks of immunotherapy?

The risks of immunotherapy depend on the type and purpose of the treatment, but generally speaking, immunotherapy can cause side effects that affect your immune system and other organs. Some of the risks of immunotherapy are

Immunotherapy can cause allergic and inflammation-related reactions. Even the doses of allergens in immunotherapy are low, those with severe allergies can still suffer from an allergic reaction or an inflammation-related reaction in your body. These reactions can range from mild to severe or even life-threatening, and they can happen during or after the treatment. Some of the symptoms of these reactions include rash, itching, swelling, difficulty breathing, low or high blood pressure, fever, chills, nausea, vomiting, diarrhoea, headache, fatigue and organ damage. You should tell your doctor or nurse right away if you experience any of these symptoms during or after immunotherapy.

Immunotherapy may not work for everyone. Immunotherapy is not a one-size-fits-all treatment. It may work better for some people than others, depending on their type of allergy, their genetic makeup, their immune system status and their response to previous treatments. Immunotherapy may not be suitable for everyone and may not be available for every type of allergy.

How effective is immunotherapy for insect stings?

VIT is the most common immunotherapy for insect venom allergies.

Immunotherapy for insect venom allergies can last months to years depending on the type of allergy and what symptoms were previously experienced. It can be beneficial in seeing a reduction in medication and prevention of anaphylaxis. For those with anaphylaxis to insect bites and stings there is an increased risk of anaphylaxis and other localised allergic reactions in the injection (shot) site.

VIT has been shown to reduce the risk of anaphylaxis from 60% to less than 5%.

How effective is immunotherapy for hayfever?

SCIT and SLIT are the most common immunotherapies for hayfever allergies and allergic rhinitis.

Immunotherapy for pollen allergies can last months to years depending on the type of allergy and what symptoms were previously experienced. It can be beneficial in seeing a reduction in medication and prevention of anaphylaxis. Certain pollen allergies like grass and ragweed respond better to immunotherapy than other types of pollen.

In a recent study SLIT tablets were superior to SCIT in terms of safety, but slightly less effective than SCIT.

How effective is immunotherapy for asthma?

SCIT and SLIT are the most common immunotherapies for allergic asthma.

Immunotherapy for allergic asthma can last months to years depending on the type of allergy and what symptoms were previously experienced. It can be beneficial in seeing a reduction in medication and prevention of severe asthma attacks.

Uncontrolled or severe asthma is usually a contraindication in other immunotherapies, but in the small number of cases where there is only one trigger (aeroallergens like dust mites or grass pollen) SCIT and SLIT are both effective.

How effective is immunotherapy for food allergy?

SCIT, EPIT and OIT are the most common immunotherapies for food allergies.

Immunotherapy for food allergies can last months to years depending on the type of allergy and what symptoms were previously experienced. It can be beneficial in seeing a reduction in medication and prevention of anaphylaxis. For those with anaphylaxis to food allergens there is an increased risk of anaphylaxis and other localised allergic reactions in the mouth and throat.

Various studies have shown EPIT to have 35 to 67% effectiveness in reduction of symptoms. This is higher in children under the age of 11.

Because of the mode of delivery of the allergen, OIT for food allergies is linked to a higher incidence of adverse effects like anaphylaxis or severe allergic reactions. In most European countries it is only offered for peanut, cow milk and egg allergies. It is not recommended for people who suffer from multiple severe allergies with anaphylaxis.

How effective is immunotherapy for pet allergies?

SCIT and SLIT are the most common immunotherapies for pet allergies.

Immunotherapy for food allergies can last months to years depending on the type of allergy and what symptoms were previously experienced. It can be beneficial in seeing a reduction in medication and prevention of anaphylaxis. For those with anaphylaxis to pet dander and other allergens there is an increased risk of anaphylaxis and other localised allergic reactions in the mouth and throat with SLIT.

SLIT has proven to be effective in reducing symptoms in those with pet dander allergies.

How long does immunotherapy take?

The duration of immunotherapy depends on the type of treatment but can take from several months to several years to complete. Some of the factors that affect how long immunotherapy takes are

The type of immunotherapy.
Each type of immunotherapy has its own schedule and frequency of administration, ranging from daily to monthly or longer.

The type of allergy.
Immunotherapy may work better for some types of allergy than others. Immunotherapy may not be suitable or available for everyone or every type of allergy.

The phase of treatment.
Immunotherapy usually has two phases: the build-up phase and the maintenance phase. The build-up phase involves giving gradually increasing doses of the immunotherapy allergen to help the immune system tolerate it and not react to it so strongly. The maintenance phase involves giving a stable dose of the allergen to keep the immune system active and prevent relapses or complications. The build-up phase can take from several weeks to several months, while the maintenance phase can take from several months to several years or longer.

The individual response and preference.
Some people may experience improvement sooner than others, while some people may experience side effects or reactions that require additional treatments or medications to manage them. Some people may prefer to continue or stop immunotherapy based on their personal goals and preferences.

In Conclusion

Please make sure that you are aware of the possible side effects and reactions that may occur during or after immunotherapy as well as the benefits. Immunotherapy for allergies can improve your quality of life and reduce your dependence on medication, but it requires commitment and patience.

References

Allergy UK Immunotherapy
Drugs.com - Does Immunotherapy Work?
DermNet NZ - Immunotherapy for Allergic Diseases
Science Direct - Immunotherapy
Science Direct - SLIT
Science Direct - SCIT
Science Direct - Oral Immunotherapy
Anaphylaxis Campaign - Venom Immunotherapy
ASCIA - Venom Immunotherapy - A Guide for Clinical Immunology/Allergy Specialists
British Society for Allergy and Clinical Immunology
FARE (US) - EPIT


Real-World Multi-Food Home Oral Immunotherapy Using Daily Micro-Dose Schedules Has Low Rates of Adverse Reactions, 2024
Update on oral and epicutaneous immunotherapy for children with food allergy, 2023
Efficacy and safety of sublingual immunotherapy for allergic rhinitis: A network meta-analysis, 2023
Allergen immunotherapy for food allergy: Evidence and outlook, 2022
Honey bee venom re-challenge during specific immunotherapy: prolonged cardio-pulmonary resuscitation allowed survival in a case of near fatal anaphylaxis, 2022
Use of Sublingual Immunotherapy for Aeroallergens in Children with Asthma, 2020
Allergen immunotherapy for asthma prevention: A systematic review and meta-analysis of randomized and non-randomized controlled studies, 2022
Safety and efficacy of venom immunotherapy: a real life study, 2017
Epicutaneous immunotherapy, 2017
Allergen immunotherapy for insect venom allergy: a systematic review and meta-analysis, 2016


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