Background: Experimental data demonstrate that incite allergy is characterized by persistent chronic inflammation, even during asymptomatic periods. This suggests that long-term continuous treatment be included in the global strategy of allergy treatment. Objective: We conducted a study to evaluate whether regularly administered cetirizine reduces allergic symptoms and drug prescriptions in children with mite allergy. Methods: In this double-blind, randomized, placebo-controlled study, two parallel groups of 10 children with mite allergy (mean age: 6.5 years) received either cetirizine or placebo daily for 6 months. Participants were allowed to take rescue medications for rhinitis and/or mild asthma. The symptoms (nasal itching, sneezing, obstruction, rhinorrhea, conjunctival itching, lacrimation, conjunctival hyperemia, cough, wheezing, and chest tightness) were recorded on a diary card. The intake of cetirizine (as additional symptomatic treatment), antibiotics, acetaminophen, beta (2)- agonists, inhaled and systemic corticosteroids was also recorded. Results: Symptom scores and drug consumption were significantly lower (P < 0.05) in the cetrizine-treated group versus the placebo group. The greatest reductions were in cetirizine itself, inhaled corticosteroids, <beta>(2)-agonists, and antibiotics. No side effects were reported in either group. Conclusions: In mite-allergic children, cetirizine administered daily for prolonged periods decreases symptoms of and drug prescriptions for allergic rhinitis and asthma compared with symptomatic treatment.