At present current knowledges on OIT are controversial. We studied the effectiveness and the possible immunological mechanisms of this therapy. We followed a group of 56 children affected by allergic asthma due to Dermatophagoides during their treatment with OIT. Many clinical parameters were investigated and also immunoallergological and spirometric values in a subgroup. We observed a particularly satisfying clinical and respiratory improvement, while immunoallergological parameters did not suffer significant changes.