In this study Predy and colleagues randomized 323 study subjects to receive a proprietary ginseng ( Panax quinquefolius ) preparation or a placebo and followed them for 4 months during the winter (September to April). Using predetermined criteria to determine if subject-reported symptoms were 'colds,' the authors found that ginseng reduced the frequency of colds. Subjects in the ginseng group reported having 2 or more colds less often than subjects in the placebo group (10% v. 23%). Symptom severity and duration were also lessened.
Folk and herbal remedies are often used in the hope that they will prevent the common cold or reduce the severity and duration of symptoms. Yet, few of these compounds are evaluated scientifically.
In a related commentary, Ronald Turner of the University of Virginia School of Medicine recently evaluated Echinacea angustifolia as a preventive herbal product for the common cold (and found it did not work). He cautions physicians and the public about the difficulties of doing clinical studies of common viral infections, especially when the specific viruses are not identified.