Experimental data demonstrate that mite allergy is characterized by persistent chronic inflammation. This suggests that long-term continuous treatment may be included in the global strategy of allergy management as recently reported. Moreover, most of allergic subjects show polysensitisation. We conducted a study to investigate whether a long-term cetirizine treatment may reduce the occurence of new sensitisations in children with mite allergy. This study was initially double-blind, randomized, and placebo-controlled, with two parallel groups of 10 children with mite allergy receiving either cetirizine or placebo daily. All children could assume cetirizine as rescue medication (i.e. symptomatic treatment). After six months, parents of continuously-treated children decided to continue the treatment for 3 years. Other subjects continued to assume cetirizine on symptomatic basis. All children were prospectively followed for other 3 years. Outcome measure was skin prick test, yearly performed. Cetirizine-continuously-treated group showed a significant lower incidence of new sensitisations (p = 0.002). In conclusion, cetirizine administered daily for prolonged periods (i.e. 3 years) may decrease the development of new sensitisations in monosensitised children, showing a potential effect of tertiary prevention of allergy.