Information for patients undergoing injection immunotherapy (desensitisation)

Desensitisation (or immunotherapy) to pollen is a highly effective treatment for hay fever. The effect of the treatment is to reduce your allergy symptoms and requirements for additional anti-allergy medication. Desensitisation is only considered if all other treatments are shown to have been ineffective and should not be considered a first-line treatment because of the risks involved, as well as the time commitment and cost.

Procedure

Desensitisation involves regular injections under the skin of your arm. There are various regimens, which are dependent on the allergen being used. Either four or six injections will be administered weekly before the onset of the hay fever season. We will start by giving you a small dose of allergen in the first week and then gradually increase the dose in subsequent weeks of the course of treatment. This course of treatment is carried out before each pollen season for three years. The most appropriate form of treatment will be discussed with you. A sublingual grass pollen treatment is also an option in some patients. This consists of a daily tablet taken under the tongue for three years.

Before each injection, you will have your pulse, blood pressure and peak flow (a respiratory test) measured by the nurse. The doctor will then ask you questions about your general health and whether you experienced an allergic reaction with any previous injections. After you have been injected it is necessary to remain in the Clinic under observation for one hour. During this period, you may have further measurements of your pulse, blood pressure and peak flow.

Side effects

The injection site may become slightly swollen and itchy for a few hours, but in some cases the swelling may last up to two to three days, but these reactions generally improve once the top dose is reached. Some patients develop tiredness for up to 24 hours after the injection especially with the first few injections. Rarely, small nodules may appear under the skin at the site of injection. These do not harm and the treatment may be continued. Occasionally, more serious reactions can occur such as a generalised itchy rash, asthma, itchy eyes or nasal symptoms. All these are readily treatable.

Severe allergic reactions

Sometimes, a severe allergic reaction can occur soon after the injection and will be treated quickly by the Clinic doctor. Severe allergic reactions are the reason why it is necessary to have this form of treatment in a specialised Allergy Clinic run by staff highly trained in the treatment of allergy.

Effectiveness of desensitisation

Allergen desensitisation is highly effective and the majority of patients will benefit. However, long-term improvement is only seen if you complete the full course of treatment which usually takes three years.

Contraindications

If you have asthma you will be at greater risk of a severe allergic reaction to the treatment and therefore desensitisation may not be safe. Your allergy doctor will discuss this with you.

Other medications

It is very important that you tell the doctor which medications you are taking or if you start a new drug during the desensitisation period. Most drugs can be continued during desensitisation but some, for example, beta-blockers that are often prescribed for blood pressure or heart conditions should be stopped before treatment is started.

Precautions after an injection

Exercise can increase absorption of allergen from the injection site leading to an increased risk of side effects. We would therefore recommend that vigorous exercise such as cycling home or taking part in any activity that involves strenuous use of your arms should not be undertaken for 24 hours after the injection. Injections should not be given at the same time as vaccinations. It is usually recommended leaving a week between vaccinations and immunotherapy injections.

If you are unwell

If you are unwell with a cold, flu or have a fever for any other reason your injection will be postponed until you recover. Please contact the allergy secretaries on 01223 217777 before your appointment.

Similarly, if your allergic symptoms have started or if you experience significant asthma, the injection dose may be either reduced or delayed.

Pregnancy

Desensitisation is not usually started during pregnancy or if you are trying to conceive because of the risk to the baby should a severe reaction occur. However, in some circumstances, desensitisation may be continued during pregnancy particularly if you are at an advanced stage of treatment and have not experienced any allergic reactions.

My Chart

We would encourage you to sign up for MyChart. This is the electronic patient portal at Cambridge University Hospitals that enables patients to securely access parts of their health record held within the hospital’s electronic patient record system (Epic). It is available via your home computer or mobile device

More information is available on the My Chart information section on our website.