Oral antihistamines for the symptom of nasal obstruction in persistent allergic rhinitis - A systematic review of randomized controlled trials

Background: Oral antihistamines are recommended by a World Health Organisation working group as a first-line pharmacological treatment in mild persistent allergic rhinitis. There is, however, uncertainty with respect to their effectiveness for a common symptom, that of nasal obstruction. Objective: To test the null hypothesis that oral antihistamines have no effect on the symptom of nasal obstruction in a clinical setting in patients with persistent allergic rhinitis. Methods: Protocol based review of double-blind randomized controlled trials of oral antihistamine (i.e. drugs considered to act as a histamine receptor type-1 antagonist) vs. placebo. A search was carried out for published and unpublished trials. Individuals had to be age 12 years or older (with a diagnosis confirmed by skin prick tests, IgE blood tests or nasal allergen challenge), experiencing their normal allergen exposure. A symptom score for nasal obstruction had to be recorded. Predetermined quality criteria were applied. Treating their data as 4-point scores, a meta-analysis was carried out for studies, which provided enough data to be pooled. Results: Meta-analysis found a weighted mean difference of -0.52 in favour of treatment for patient-assessed symptom scores (95% confidence interval (CI) -0.73, -0.31, P<0.00001), and of -0.33 in favour of treatment for healthcare worker assessed scores (95% CI -0.49, -0.16, P = 0.0001). Conclusion: Oral antihistamines cause statistically significant improvement in the symptom of nasal obstruction in patients with persistent allergic rhinitis.