A Cochrane review included 3 therapeutic studies with a total of 182 subjects and 4 safety studies with a total of 3 166 subjects. The studies varied in age of subjects, sample size, inclusion criteria, type of anti-histamine and length of intervention. In one study, children with recurrent wheeze were also included. The two larger studies described significant improvement in both the intervention and the placebo/placebo-like arms with no significant difference between the two groups. In the study with the smallest sample size, cetirizine was significantly more efficacious than placebo in reducing chronic cough in children associated with seasonal allergic rhinitis, and the effect was seen within 2 weeks of therapy.
In the safety evaluation studies cough as an adverse event occurred more frequently in the active arms than in the placebo arm although the difference was not significant (OR 1.47, 95% CI 0.86 to 2.49).
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals) and by indirectness (differences in studied patients and interventions)