Background Specific immunotherapy (SIT) is a recognized way of treating IgE‐mediated respiratory diseases. The clinical outcome is usually better in allergic children than in adults.

Objective To increase our knowledge of the ability of SIT to prevent the onset of new sensitizations in monosensitized subjects, so far poorly documented.

Methods 134 children (age range 5–8 years), who had intermittent asthma with or without rhinitis, with single sensitization to mite allergen (skin prick test and serum‐specific IgE), were enrolled. SIT was proposed to all the children's parents, but was accepted by only 75 of them (SIT Group). The remaining 63 children were treated with medication only, and were considered the Control Group. Injective SIT with mite mix was administered to the SIT Group during the first three years and all patients were followed for a total of 6 years. All patients were checked for allergic sensitization(s) by skin prick test and serum‐specific IgE every year until the end of the follow‐up period.

Results Both groups were comparable in terms of age, sex and disease characteristics. 123 children completed the follow‐up study. At the end of the study, 52 out of 69 children (75.4%) in the SIT Group showed no new sensitization, compared to 18 out of 54 children (33.3%) in the Control Group (P < 0.0002). Parietaria, Gramineae and Olea were the most common allergens responsible for the new sensitization(s).

Conclusions According to our data, SIT may prevent the onset of new sensitizations in children with respiratory symptoms monosensitized to house dust mite (HDM).