Information for Patients Undergoing Venom Desensitisation

Desensitisation (or immunotherapy) is a highly effective treatment for severe bee and wasp sting allergy. Desensitisation is only considered for severe reactions if you remain at high risk of being stung in the future. The effect of the treatment is to substantially reduce your allergic reaction to future stings, by giving small amounts of the allergen (a substance that causes an allergy) at safe intervals.

Procedure

Desensitisation involves regular injections under the skin of your arm. Increasing amounts of bee or wasp venom is given weekly for 8-10 weeks until the top dose is achieved. This is followed by injections at 8-10 week intervals at the top dose for a further three years.

Before each injection, you will have your pulse and blood pressure measured by the nurse. A doctor or a specialist nurse in Allergy will then ask you questions about your general health and whether you developed an allergic reaction with any previous injections. The doctor or nurse gives the injection in the outer aspect of the upper arm. You may experience some discomfort at the site of the injection. After your injection, it is necessary to remain in the clinic under observation for one hour. During this time, you will have further measurements of your pulse and blood pressure. At intervals during the three-year desensitisation you will be asked to have a blood test to monitor the specific antibodies to venom.

Side effects

The injection site may become slightly swollen and itchy for 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 during the first two months. Less commonly, reactions that are more serious can occur such as a generalised itchy rash, asthma, itchy eyes or nasal symptoms. All these are readily treatable.

Severe allergic reactions

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

Effectiveness of desensitisation

Bee and wasp venom desensitisation is highly effective (85-95%) and the majority of patients will benefit. However, long-term improvement is only seen if you complete the three-year course of treatment.

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 dose alteration may be required for beta- blockers, which are often prescribed for blood pressure, migraine or heart conditions during the initial up dosing period. Your doctor will discuss these requirements before starting venom immunotherapy course

Precautions after an injection

Exercise can increase absorption of allergen from the injection site and can lead to 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.

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 clinic on 01223 216645/217777. Similarly, if you have other allergic symptoms, which have become worse recently, for example hay fever or asthma, the injection dose may be either reduced or postponed.

Pregnancy

Desensitisation is not usually started or continued during pregnancy because of the risk to the baby should a severe reaction occur.