What is allergen immunotherapy?

Allergen immunotherapy is a way to prevent or minimise allergies by switching off the body’s reaction to substances that cause allergic reactions. Allergen immunotherapy can take years to work.

Allergen immunotherapy is a way to change the way your body reacts to things you are allergic to (allergens). Unlike other allergy medicines, which reduce symptoms, immunotherapy is the closest thing we have to a ‘cure’ for allergies.

An allergic reaction occurs when your body’s immune system responds to something that is normally 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 become immune to the allergens and don’t react to them anymore.

How is allergen immunotherapy given?

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

• Injections — a very small dose of the allergen is given with a small needle, which should not hurt. You usually need weekly injections at first and the dose is gradually increased over 3 to 6 months until a 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 the immunotherapy at home and there is less chance of side effects. However, this is more expensive and for some types of allergy 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, you should continue to take your allergy and asthma medicines as usual.

Which allergies can allergen immunotherapy treat?

Allergen immunotherapy is usually recommended to treat:

• potentially life-threatening allergies to stinging insects such as 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 adequately
• dust mite allergy
• asthma, if you know your symptoms are caused by a specific allergen that's hard to avoid
• eczema

Allergen immunotherapy has not been shown to work for food allergies, although research into this is still going on.

Both 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 allergic rhinitis will have a significant improvement in their symptoms (blocked or runny nose, sneezing, and itching) and enjoy a better quality of life after allergen immunotherapy.

Allergen immunotherapy has also been shown to have lasting benefits for asthma — as long as you know which allergen is responsible for your asthma symptoms. It can also prevent children with allergic rhinitis from developing asthma.

What are the risks of allergen immunotherapy?

Some people experience a 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 normally have to stay in the doctor's surgery for 30 minutes after treatment and avoid exercising for a few hours. Taking an antihistamine first may reduce the chance of side effects.

If you have sublingual immunotherapy, you may have minor swelling or itching inside your mouth, or an upset stomach. Serious side effects are very rare.

Resources and support

Allergen immunotherapy should always be done by a clinical immunologist or allergy specialist.

For more information, visit the Australasian Society of Clinical Immunology and Allergy (ASCIA) website.