What is allergen immunotherapy?

Allergen immunotherapy is a way to change how your body reacts to things you are allergic to (allergens). Unlike other allergy medicines, which reduce symptoms, immunotherapy is used to treat allergies directly.

Allergen immunotherapy can prevent or reduce allergies by switching off your body's reaction to things that cause allergic reactions. It can take years to work.

An allergic reaction happens when your body's immune system responds to something that is usually harmless. Allergen immunotherapy works by regularly introducing tiny doses of the allergen to the body over several years. The immune system gradually 'switches off' so you don't react to the allergen anymore.

How is allergen immunotherapy given?

Allergen immunotherapy is given via injections under the skin, as oral tablets, oral sprays or drops under the tongue.

• Injections — a very small dose of the allergen is given with a small needle. These injections don't usually hurt. At first, you usually need weekly injections. The dose is gradually increased over 3 to 6 months, until a steady (maintenance) dose is reached. You will then need regular injections, usually once a month, for several years.
• Under the tongue (sublingual) — sublingual immunotherapy is given in tablets, sprays or drops. You keep the allergen under your tongue for a few minutes and then swallow it. You can take this type of immunotherapy at home and there is less chance of side effects. This is more expensive and for some types of allergies it isn't as effective as injections.

Symptoms usually start to improve after about 4 to 5 months. During this time, you must keep taking the immunotherapy regularly and work closely with your doctor. It's usually recommended to keep up the treatment for 3 to 5 years to prevent the allergies returning.

While you are having allergen immunotherapy, continue to take your allergy and asthma medicines as usual — your doctor will guide you.

Allergy immunotherapy should always be done under the supervision of a clinical immunologist or allergy specialist.

Which allergies can allergen immunotherapy treat?

Allergen immunotherapy may be recommended to treat:

• potentially life-threatening allergies to stinging insects like bees, wasps and jack jumper ants
• hay fever (allergic rhinitis) caused by pollen or dust mite allergy, when symptoms are severe and medicines aren't working well enough
• asthma, if you know your symptoms are caused by a specific allergen that's hard to avoid
• eczema (in rare cases)

Allergen immunotherapy is not currently used in Australia to treat food allergies due to limited evidence for its effectiveness, although research into this is ongoing.

Children and adults can have allergen immunotherapy, although it can be hard to get very young children to cooperate. The treatment is also not suitable for people with some medical conditions, such as heart disease.

How successful is allergen immunotherapy?

Allergen immunotherapy has been in use for more than 100 years. Sublingual immunotherapy is a newer treatment that has become much more effective over the past 10 years.

Research shows allergen immunotherapy can reduce the chance of someone having a severe reaction to stinging insects from about 6 in 10 to less than 1 in 10.

Almost everyone with hay fever who has immunotherapy will have improvement in their symptoms. Most people also experience a better quality of life after allergen immunotherapy.

Allergen immunotherapy can have lasting benefits for asthma, if you can identify the allergen responsible for your asthma symptoms. It can also prevent children with hay fever from developing asthma.

What are the risks of allergen immunotherapy?

Some people experience swelling at the site of the injection. The greatest risk is a severe allergic reaction (anaphylaxis), although this is very rare.

Just in case, you will have to stay in the doctor's surgery for 30 minutes after treatment with allergen immunotherapy, and not exercise for a few hours. Taking an antihistamine before treatment may reduce the chance of side effects.

If you have sublingual immunotherapy, you may have a small amount of swelling or itching inside your mouth, or diarrhoea. Serious side effects are rare.

Resources and support

For more information about how allergen immunotherapy works, when it is recommended and how it is given, visit the Australasian Society of Clinical Immunology and Allergy (ASCIA) website.

Visit Allergy Anaphylaxis Australia for information and support on treatment of allergy.

Call healthdirect on 1800 022 222 at any time to speak to a registered nurse (known as NURSE-ON-CALL in Victoria) for more information and advice.