Sixteen studies (n=1,561, range 16 to 330) were included in the review. The median Jadad score was 4 (range 2 to 4). In all studies the herbal medicine under evaluation was the only treatment; five studies allowed the use of rescue medication.
Petasites hybridus (six studies): Three placebo-controlled studies found that P. hybridus may be effective for relief of symptoms or improved peak nasal inspiratory flow. Two studies that compared P. hybridus with non-sedating antihistamine and one that comparing it with placebo found no significant differences between treatments for any outcomes.
Aller-7 (two studies): Two placebo-controlled studies of Aller-7 found reductions in measures of individual symptoms compared with placebo. One also found a significant reduction in total nasal symptom score.
Chinese herbal medicine (three studies): One study found statistically significant differences for the overall therapeutic effect (sneezing, stuffy nose and running nose) of a compound of eight different herbs compared with placebo. Biminne (11 herbs) significantly reduced sneezing compared with placebo and showed a non-significant reduction in other weekly symptom scores over time. An extract of 18 herbs showed a statistically significant difference compared with placebo for change in symptoms (measured on a 5-point scale) after five weeks and for quality of life after seven weeks.
Other herbal preparations (five studies): Studies of other herbal preparations compared with placebo found statistically significant effects for Tinospora cordifolia for symptoms (nasal discharge, sneezing and nasal obstruction and itching) and Perilla frutescens for quality of life. Other studies either found no significant differences or did not perform any statistical analyses.
Adverse events: 11 studies reported adverse events, most were minor including fatigue, nausea and indigestion, but there were a few reports of severe events prompting patient withdrawal from the study.