Immunotherapy is an empirical treatment with proven clinical efficacy. Different results have been found when comparing the levels of the subclasses for immunoglobulin G and the clinical development during immunotherapy. A follow up study was carried out for one year on the IgG subclasses in 21 asthmatic children of both sexes and ages ranging from 8 to 11 years. The children were sensitized to Dermatophagoides Pteronyssinus and had undergone immunotherapy treatment. The clinical and analytical evaluation were carried out before treatment was started and later every four months. In terms of clinical evolution, the children were separated into two groups. The levels of IgG1 show different evolution in terms of a good or not good clinical evolution with a p of 0.056. Levels of IgG2 showed no differences. IgG3 shows a disorderly distribution. A continuous increase in IgG4 levels was observed from the start of immunotherapy though no differences in terms of clinical evolution were recorded. With the results obtained, it can be concluded that the gradual increase of IgG4 together with an early rise in IgG1 levels are related to the clinical efficacy of immunotherapy.