Immunotherapy

Immunotherapy or "desensitisation" is a treatment to make a person less allergic, or more tolerant to the substance to which they are allergic. It is used for allergies to inhaled substances that cause hay fever and asthma, such as grass pollens, house dust mite or animal dander. Immunotherapy is also very effective for stinging insect venom allergy. Immunotherapy has not been shown to be safe nor uniformly effective for food allergies and is not offered.

How is Immunotherapy given?

Immunotherapy can be given by injection (subcutaneous immunotherapy) or in the mouth (under the tongue (sublingual immunotherapy). In injection immunotherapy the process is to slowly build up the dose of allergen and then to continue with a dose which will cause the immune system to tolerate the substance. These maintenance injections for immunotherapy are usually given every month.

Sublingual immunotherapy (by mouth, under the tongue) is best given by tablets which are now available for house dust mite and grass pollens. There is little or no up-dosing phase with these tablets. Sublingual drops are available for other allergens such as animal allergy. Sublingual immunotherapy is given daily at home and the tablets are quite portable so they are fine to take while travelling.

Immunotherapy usually is prescribed for 2 to3 years, longer in the case of insect venom immunotherapy as this causes a durable remission in symptoms. It is usual to see a response after 6 months.

How effective is Immunotherapy?

Immunotherapy is the closest thing we have to a cure for allergies. Whilst it usually doesn’t make symptoms go away completely, it usually reduces symptoms substantially, often by about two-thirds. When used for allergic rhinitis (hay fever) it does provide additional benefit over antihistamines and corticosteroid nose sprays. The benefits of a 3-year course of immunotherapy should last for 5 to 8 years. Sublingual immunotherapy, although a newer treatment, has similar benefits although some recommend a longer treatment duration, perhaps as much as 4 years of maintenance treatment.

Immunotherapy will not cure asthma, but it will likely help asthma. There is good evidence that sublingual immunotherapy can reduce asthma exacerbations and may enable a reduction in preventer medications. However immunotherapy should only be given when asthma is well-controlled, and does not replace asthma preventer treatments.

Who should consider immunotherapy?

Severe allergies to insect venom are an absolute reason to undertake immunotherapy, as this is a life-saving treatment.

In the case of respiratory allergies such as hay-fever there are a few reasons to consider immunotherapy:

1. Anyone with significant allergic nose or eye symptoms to an inhaled substance that is not well controlled with medication
   
2. Where the medications required are burdensome or not tolerated
   
3. Where the person chooses to undertake immunotherapy for management of their disease.

What are the side-effects of immunotherapy?

In subcutaneous immunotherapy (by injection) about 25% of people will develop a red lump at the site of injection which nearly always goes away after a couple of hours. Sometimes these reactions are larger and in this case the up-dosing schedule may need to be modified.

More serious allergic reactions can occur which involve a general allergic reaction such as hives. asthma or even anaphylaxis. These severe reactions occur in about 1:100,000 injections for inhaled substances and can be life-threatening. Because of this risk it is critical that all injections are given at a doctor's surgery and the person receiving the immunotherapy injection waits in the doctor’s room for 30 minutes after each allergy injection. Injections should not be given to people with unstable asthma, so let your doctor know if you are not well and best practice is to check the peak flow before each injection and make sure it is close to your best. Usually however, injections are safe and well-tolerated and part of a specialist allergy consultation is deciding who is able to receive this treatment safely.

Sublingual immunotherapy (by mouth) usually gives a feeling of itch or swelling under the tongue for the first few doses, although this can last a few weeks at the start of treatment. However overall sublingual immunotherapy does not appear to cause the severe reactions that are recognised to occur with injection immunotherapy. Sublingual tablets or drops must be taken every day, which some people find inconvenient and difficult to remember.

Whilst immunotherapy is not recommended in pregnant women, no evidence of harm due to immunotherapy has been described. Our practice is to cease immunotherapy if you become pregnant.

How much does it cost?

At the current time immunotherapy injections and sublingual tablets or drops are not paid for on the Pharmaceutical Benefits Scheme, with the exception of stinging insect venoms for immunotherapy. So this means patients must meet the whole cost of treatment. Injection immunotherapy is less expensive than sublingual immunotherapy with the cost per kit of approximately $270 and about 3 or 4 kits are required over the time of the immunotherapy. Sublingual immunotherapy costs about $100-$150 per month. Grass pollen allergies can be treated for half the year, but house dust mite or other year round allergies require treatment continually so this will cost approximately $1200 per year. Some private insurance extras schemes reimburse some of these costs.

How do I choose which form of Immunotherapy?

The role of a specialist allergist is to determine which substances are causing the majority of your symptoms and to prescribe the Immunotherapy. The choice between sublingual and injection therapy is one that can be made during your consultation by considering the type of allergy, the cost, treatment burden, side effects and safety as well as the effectiveness of both methods.

What about the future?

This is a rapidly developing area with some really exciting new treatments being developed and trialled in Australia. If you are interested in being involved in trials of Immunotherapy treatments, let your doctor know.

More information

Australasian Society of Clinical Immunology and Allergy (ASCIA) - Allergen Immunotherapy

  Make an appointment with Melbourne Allergy Asthma & Immunology Consultants to find out if immunotherapy is right for you.