For many years, immunotherapy (hyposensitsation) proved to be the only ´causative´ treatment of pollen allergy. In general, very good results are reported - about 90% of the treatments give satisfactory results or total relief. The mechanism is still not exactly known. The principle is to permanently confront the immuno system with low doses of the respective specific allergen in order to accustom the body to the presence of this allergen. By the time, the immuno system gives up the excessive reaction. In fact, the treshold line rises in the course of several years, and the patient tolerates normal pollen loads without having allergic reactions.
Treatment takes time. Three to five years are necessary to reach the optimum. As the body could react with an anaphylactic shock to higher doses of allergen solution, increasing doses are injected weekly at the beginning of treatment in order to reach the effective dose after approximately ten weeks. After this period of preparation, a monthly injection will be applied. During the respective pollen season treatment will be either interrupted or continued with strongly reduced dose. Of course, immunotherapy shall be supported by antiallergic drugs, avoiding or minimizing pollen contact and all possible actions to fight the symptoms.
In the course of the years, the therapy solutions have been standardised and purified. They are extremely safe compared to those which were available in former times.
The risk of adverse reactions is low. Mainly they are confined to local reactions like swelling of the spot where the injection has been applied to, or an erythema on this place. However, as an anaphylactic shock could happen in the worst case (much too high dose or injection into a blood vessel), the patient must stay under observation half an hour after each injection. In case of adverse reactions which are expected within this time, the doctor can help immediately, but without medical aid it could become fatal. If the treatment is carried out by a responsible allergologist, the hazard of side effects is practically zero.
During the past years, other forms of application have been developed, such as oral (sublingual) intake or even application of the allergen extract as a nasal spray. In the majority of cases, they show comparable results, but they have to be applied more often than injections. The phase of increasing doses needs daily application, and the treatment itself has to be continued three times a week. The whole period of treatment lasts three to five years, exactly like the injection therapy.
In many cases, patients consult their doctor not before their symptoms have become intolerable. In such cases, a new method is in trial to allow seasonal specific immunotherapy. The intervals of dose increase during the initial phase of immunotherapy may be shortened down to 1.5 hours, both with conventional "allergy shots" and sublingual immunotherpy. First results look promising.
Children below five years of age are seldom treated.