Objective: To evaluate the efficacy of herbal medicines for the treatment of allergic rhinitis (AR).
Data sources: Five electronic databases until November 8, 2005; bibliographies of located articles; manufacturers of commercially available preparations; and experts in the field.
Study selection: We only included double-blind randomized clinical trials (RCTs), which tested a herbal medicine against placebo or active comparator, in patients with AR, and evaluated clinically relevant outcomes. Study selection, data extraction, and evaluation of methodological quality were performed independently by 2 reviewers. Discrepancies were resolved by discussion and by seeking the opinion of the third reviewer. Meta-analysis was only performed if data were considered suitable for pooling.
Results: Sixteen eligible RCTs, testing 10 different herbal products against placebo or active comparator, were included. Six RCTs studied Petasites hybridus (butterbur) extract for AR and suggest that P hybridus is superior to placebo or similarly effective compared with nonsedative antihistamines for intermittent AR. Two RCTs studied an Indian herbal combination, Aller-7, in patients with AR and reported positive results. Single RCTs were identified for 8 other herbal products as treatments for AR, reporting positive outcomes, except for grape seed extract. The median methodological quality score was 4 of a possible maximum of 5.
Conclusions: There is encouraging evidence suggesting that P hybridus may be an effective herbal treatment for seasonal (intermittent) AR. However, independent replication is required before a firm conclusion can be drawn because of the financial support from the manufacturer of P hybridus extract to the 3 large trials. There are also promising results generated for other herbal products, particularly Aller-7, Tinospora cordifolia, Perilla frutescens, and several Chinese herbal medicines. Although these results are confined to the paucity of data and the small sample size, confirmation in larger and more rigorously designed clinical trials is warranted.