Herbs and other dietary supplements: current regulations and recommendations for use to maintain health in the management of the common cold or other related infectious respiratory illnesses.

Herbal preparations are sold as dietary supplements in the United States and are subject to the rules and regulations of various health care and economic government agencies that monitor the sale of these products. One approach to assessing the usefulness of these substances is to focus on one particular disease state and then review both the primary literature and expert opinion. The common cold is an important illness due to its recurring nature, the number of people it afflicts, and its economic impact on patients. Dietary supplements have been shown to decrease the duration, the severity, and the frequency of symptoms of the common cold. The most commonly available supplements are zinc, ginseng, echinacea, and vitamin C. Data from expert opinion suggested that certain supplements are more beneficial than others to maintain one's health during episodes of the common cold. Expert opinion regarding the use of dietary supplements in other related infectious respiratory illnesses, such as the flu, when aggregated with expert opinion findings regarding the common cold were not contradictory. The primary literature provided insights into specific dosages and compounds that may be used in practice.