Immunotherapy - a treatment for severe allergies

What is Immunotherapy?

Immunotherapy (IT) is a well-established treatment for certain severe allergies. The World Allergy Organisation defines it as 'the repeated administration of allergen vaccines to allergic individuals in order to provide long term relief of symptoms and improvement in quality of life'.

Allergy develops when the immune system mistakenly makes antibodies (IgE) to 'fight off' a substance (allergen) that wouldn't normally bother us, such as pollen, animal dander, housedust mites, mould spores, foods or the venom of bees or wasps. Immunotherapy is an attempt to change this over-reaction of the immune system by giving the patient increasing doses of the allergen at regular intervals (starting with a very small dose) in a carefully controlled way. If successful, immunotherapy stimulates the production of 'regulatory' cells, which stop the production of IgE and produce tolerance of the allergen.

Immunotherapy is generally given by injection although new methods using drops or tablets placed under the tongue (sublingual immunotherapy) have been developed more recently and are beginning to become available.

All immunotherapy carries a degree of risk, is time-consuming and expensive. In the UK, it is generally reserved for patients with the most severe allergies and for certain types of allergy. Most allergy symptoms are relatively mild and are well controlled with medicines such as inhalers, antihistamines, steroids or other drugs, and by avoiding the trigger allergens. If these measures are effective then there is no need for immunotherapy. Most allergy clinics will not accept patients for immunotherapy unless they have tried all the usual treatments first and have taken them properly and in the right combination.

Will I benefit from immunotherapy?

Patients with certain allergies may be considered for IT:

1. Life-threatening reactions to wasp or bee stings

Sudden collapse (Anaphylactic shock) or other life-threatening reactions such as swelling of the airways.

Venom immunotherapy is highly effective, giving 98% protection against serious wasp venom reactions and 80% protection against serious bee venom reactions. An alternative treatment is to carry injectable Epinephrine (adrenaline), but this is not always a complete treatment and further medical aid may be necessary after a sting. Minor reactions, such as swelling at the site of the sting, or nettle rash (urticaria), can be treated simply.

If you have had allergic reactions to wasp or bee stings, an Allergy specialist's advice may be helpful in deciding whether immunotherapy is necessary, as the classification of reactions is complex.

There is no vaccine available for mosquito bites which rarely, if ever, cause generalised allergic reactions.

2. Severe hayfever

Normally, hayfever can be successfully controlled by treatments such as nasal sprays, antihistamines and eyedrops. Some people find these treatments ineffective. In this situation, a short course of steroid tablets may be needed.

Strategy for avoidance of severe hayfever:

Start full protective treatment well before the pollen season starts.
1. Regular steroid nasal spray.
2. Regular sodium cromoglycate or nedocromil sodium eyedrops.
3. Regular steroid inhaler, if you have asthma.
4. Regular antihistamine tablets.
5.Leukotrine-receptor antagonists if the above fail to control symptoms.

Once symptoms are established, it can be much harder to control the allergic reaction.

If you have tried the preventive approach outlined above and still need steroid tablets or have severe hayfever symptoms, then you may be a candidate for pollen immunotherapy.

3. Animal Allergies

Avoidance of the allergen is most important. If you keep pets to which you are allergic at home, you will not be considered for immunotherapy as it is unlikely to succeed when there is a background of continuous allergen exposure causing allergic inflammation.

Most people who occasionally come into contact with animal allergens can treat themselves successfully by taking antihistamines and inhalers prior to contact with the pet. For instance, if going to a friend's house where pets are kept, treatment should be started 30-60 minutes beforehand.

Immunotherapy may be indicated when a highly allergic individual is unable to control symptoms by this strategy and for those who react to the tiny quantities of allergen found on other people's clothes or in public buildings. An Allergy specialist's advice is essential in this circumstance, to determine the contribution of the allergen exposure to allergic symptoms. Occupational exposure, such as in veterinary surgeons or nurses, or in patients whose job involves visiting peoples homes, may also be considered for treatment.

Conditions for which immunotherapy is unhelpful

Multiple allergies

It is unusual for patients to receive immunotherapy for more than two allergies. Where a patient has severe symptoms caused by a number of different allergens (for example nasal symptoms caused by grass pollen, housedust mites, cats and moulds) they may be given immunotherapy for one or two of these so that symptoms are reduced to the level where they can be managed by the usual drug treatments.

Food allergies

There are currently no preparations available for immunotherapy treatment of food allergy. Some research has been carried out to 'desensitize' people with allergy to particular foods such a egg and peanut by giving them a tiny dose of the food and gradually increasing the amount over time to produce tolerance of the food. Early results are promising but this research is still in its infancy and the technique is not widely available. It must be carried out on carefully screened individuals and in controlled conditions and is not suitable for home use.

Allergic rashes

such as eczema and nettle rash cannot be treated with immunotherapy.

What does immunotherapy treatment involve?

Screening at an allergic clinic

If you and your doctor think that you may need immunotherapy, you will need to be referred to an Allergy Specialist. In some areas, this may mean travelling some distance, perhaps to a teaching hospital.

You will be asked to have some allergy tests: skin test and sometimes a blood test for allergic antibodies.

You will also need a physical examination to assess your general fitness. It is important that conditions such as uncontrolled high blood pressure and asthma are stabilised prior to commencing treatment. It is sensible to get such problems sorted out before attending the Allergy clinic, if possible.

If you are taking a beta blocker for any reason, you will need to discuss changing this for an alternative treatment.

If you have asthma...

Few asthmatics will be considered for immunotherapy. In general, the more severe your asthma, the less likely it is that you will be considered for immunotherapy. This may seem unfair but the reason is that allergic reactions to immunotherapy, although rare, are most dangerous in asthma. However, there are exceptions. Asthma which occurs only in the pollen season is suitable for pollen immunotherapy as the early part of the treatment (when there is greatest risk of reactions) will be given outside the pollen season. Asthmatics will not be turned down for bee and wasp venom immunotherapy because the risk of a life-threatening reaction to a sting outweighs the risk of any reactions during immunotherapy. However, it is important that asthma control is carefully maintained to reduce risks.

If the specialist thinks that you need treatment...

You may have to join a waiting list.

Pollen immunotherapy cannot be started during a pollen season. If your hayfever is uncontrolled by standard treatment during the current season, you may need a course of steroids from your doctor to tide you over. Ask about Allergy referral just after a pollen season to ensure that waiting lists do not reduce your chances of treatment for the following year. Treatment will need to be started several months in advance of the next pollen season.

Injections

Immunotherapy is currently most often given as a course of injections of purified allergen extracts, under the skin of the upper arm. The schedule may vary at different hospitals.

In the induction phase, injections will be given at intervals of a week or less, while allergen doses are gradually increased. Once on the maintenance dose, you will be asked to continue attending for injections every few weeks for at least 2 years. You will be asked to wait in the clinic for one hour after each injection so that if serious side effects occur they can be rapidly treated.

"Rush" immunotherapy is a rapid method of reaching the maintenance dose. Several injections may be given a day and sometimes this will require admission to hospital. This method is only used in exceptional circumstances as allergic reactions to this treatment are more common.

Individual responses to immunotherapy vary and the duration of your treatment will be tailored to your needs. Skin tests and blood tests may be used to help determine how effective your treatment is.

Itching and swelling are common reactions at the injection site, although many patients experience no reaction at all. For some patients swelling can increase over hours to days after the injection. Antihistamine tablets and an ice pack will help ease the swelling in this situation. Some patients feel tiredness or flu-like symptoms over the hours following an injection. Avoiding alcohol or strenuous activities on the day of the injection reduces the risk of side effects like these.

There were some serious reactions to immunotherapy in the past but modern immunotherapy vaccines have a good safety record. The allergen extracts are more highly purified and are administered only by highly experienced specialists in a safe environment.

Is immunotherapy dangerous?

Some new injection vaccines are becoming available which produce their desensitizing effect much more rapidly and can be given as one short course of four injections over 3-4 weeks before the pollen season, with few side-effects and good results. The same technique may also be used for immunotherapy to housedust mites and animals, which would greatly reduce the expense and time-consuming commitment required to undergo current immunotherapy regimes.

Sublingual vaccines are given either as drops placed under the tongue or as tablets allowed to dissolve under the tongue. Sublingual drops are becoming more commonly used in specialist allergy clinics but are still not widely available. One tablet version for grass-pollen desensitization is licensed for use in the UK. Treatment is started in a specialist allergy clinic where the necessary diagnostic tests are carried out and suitable patients can be identified. Once it is established that the treatment is safe for that patient, it can be continued at home by taking one tablet daily. This type of treatment works well and generally has few side effects. The current recommendation is for a 3-year course of treatment but it may be that a shorter course will be shown to be almost as effective. At the moment this treatment is expensive and is not widely used, but availability should improve over time.

Updated 09/2010