Allergen immunotherapy

Allergen immunotherapy or desensitization involves treatment with increasing doses of an allergen extract either given by injection into the skin or by a dissolvable tablet or drops under the tongue (sub-lingual immunotherapy). Unlike drug treatments for allergic disease which mask or suppress allergic reactions, immunotherapy "resets" the immune system to prevent allergic reactions. It was first used in the early 1900s.


Injection Allergen Immunotherapy

Injection under the skin was the first route used to give immunotherapy and remains the most effective form of this treatment. It involves injections of gradually increasing doses of allergen extract (which contains a carefully controlled mix of the allergen proteins of say, grass pollen) over time. For example treatment of grass pollen hay-fever might involve a series of increasing weekly doses over 12-16 weeks followed by monthly maintenance "shots".

The risk of immunotherapy is that injection of an allergen to a sensitised patient can cause a severe allergic reaction or anaphylaxis. For this reason such treatment should be given in expert centres with full support facilities, and a wait period of one hour after each injection is recommended.