This herbal supplement is most commonly used to prevent and treat colds. Several large studies have shown that echinacea is not effective at preventing colds, but that it can shorten the length of a cold—especially if you take it as soon as you get the cold. People with autoimmune disorders such as lupus, rheumatoid arthritis, multiple sclerosis, HIV/AIDS, or other disorders affecting the immune system, should not take echinacea.
Be a careful consumer. When products on the market were tested, about half of the products did not have as much echinacea as was listed on the label. Some didn't have any measurable amount of echinacea at all! Look for a brand name that you recognize and trust.