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Specific Immunotherapy (Desensitisation)
Specific Immunotherapy (SIT) has been used to treat severe seasonal or intermittent allergic rhinitis (hayfever) for many decades. It is a vaccine of the allergen to which the patient is allergic, usually grass or tree pollen which is given by injection into the upper arm. The initial (updosing) stage starts with a minute test dose, then increasing doses until a full maintenance dose is reached. Updosing injections are usually given weekly for 8 weeks followed by a maintenance dose every 6 weeks for 3 years.
This treatment is only available in NHS Allergy Clinics and is hard to obtain as the vaccines and staff costs are expensive. It is more readily given in many other countries. There is a good argument that the treatment is cost effective as those receiving it have such severe symptoms for many weeks of the year that their lives are almost on hold. Work is impossible or ineffective and driving and machinery operation dangerous even when using a combination of medications.
Of course, the time commitment for the patient is huge. Many have to travel considerable distances for the treatment and spend about two and a half hours in the clinic during the updosing period. This is because they must take antihistamine prior to treatment, have lung function assessments before and one hour after each injection. The updosing injections are divided into 2 doses and it is necessary for trained staff to observe the patient for an hour after treatment with full resuscitation facilities as there is the potential for an anaphylactic reaction. However, in the right setting and in experienced hands, the treatment is incredibly effective for very many years. Some may never need SIT treatment again.
Many years ago, maintenance doses of SIT were given in general practice but in 1986, this was stopped as the potential for serious reactions had not been appreciated until a few patients collapsed after leaving the doctors’ premises.
Research has shown that SIT treatment for children with significant hayfever may reduce the incidence or severity of asthma in these individuals. Again, most of this work was done in Europe, especially Germany.
Recently, a new form of SIT has been developed with increasing evidence of success. This is sublingual specific immunotherapy (SLIT) and is given by drops under the tongue. Updosing still is by hospital allergy specialists but maintenance doses are self administered (by the patient) at home. For those with the most severe symptoms, it is not as effective as the injected route but the side effects are also potentially less severe. These side effects are oral – tingling and swelling of the lips, tongue and mouth.
We are hopeful that this may soon be available on the NHS, though probably only in selected centres. Evidence is still needed to show a reduction in medication, hospital admission, consultations as well as increased quality of life.