Echinacea (usually E. angustifolia and E. purpurea) is a well-known herb commonly used for its immune-boosting properties. Native to the United States, Echinacea was used by the Plains Indians more than any other herb. Echinacea is useful for treating infections, and also as an immune system stimulant. It has both anti-viral and anti-bacterial properties, as well as being somewhat anti-inflammatory.

All of this makes it perfect as a tea to use when you expect to be around groups of people or to enter a place where the likelihood of encountering infection is high. It is also very beneficial if used as soon as you begin to feel ill.

The effectiveness of echinacea in treating  an illness decreases with the length of time a person is sick before they begin taking it. Using echinacea immediately or within the first 12 hours is best. If you have been sick for 4 days, it is probably too late for it to do any real good and you should consider a different herb. Additionally, it is best not to use echinacea continuously for more than 2 weeks, or intermittently for more than 2 months, or else the immune-boosting effects will be lost.  In some individuals, the immune system can even begin to be compromised if echinacea is used at fairly high doses continuously for long periods.