Desensitization or immunotherapy (ITS) is a fundamental treatment aimed at the specific allergic component of atopic asthma. The objective of treatment is to prevent antibody-antigen interactions which are generators, among others, of bronchoconstriction. The indications are essentially limited to those asthmatics sufficiently disabled (but without complications nor on long term corticosteroids or other medications in young subjects) with asthma linked to natural lung allergens whose elimination is impossible (domestic dust, mites, pollens, epithelial debris). Proceeding with intermittent repeated injections of extracts of antigen duly identified as responsible, either aqueous products or slow release preparations absorbed as an adjuvant, which allow longer periods between injections and a better clinical tolerance. Some modified extracts are suggested with the aim of reducing allergenicity while maintaining immunogenic potency. Fundamental progress has been made in the 80's is in the purification of allergens and above all in their standardization, controlling the power and the reproducibility of their effects, their duration of action and allowing an objective assessment of the efficacy of ITS in double blind multi-centre trials. The techniques themselves depend on the aqueous choice of or slow release preparation and always consists of a two stage protocol: First, induction by increasing dosage, differentiated in its duration between the traditionally slow method to achieve a maximum ceiling dose in 3 or 4 months, or of only 2 to 4 days, by the rapid or rushed method: secondly repeated maintenance doses, the top dose being chosen to maintain efficacy over several years with a regular rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)