Echinacea is an herb with the power to boost the immune system. It works on:
Colds, coughs and flu and other upper respiratory conditions, enlarged lymph glands, sore throat,Urinary tract infections,various other minor infections, wounds, skin regeneration and skin infections (external use), Psoriasis, eczema and inflammatory skin conditions (external use).
It is also thought to help combat herpes and candida.
Echinacea is more of a "traditional" or "eastern" medication which hasn't been validated too officially by the FDA, but has proven very useful for many individuals for a very long time.
Some of the specific functions of echinacea are increasing the number and activity of immune system cells, including anti-tumor cells and promoting T-cell activation. The stimulation of the T-cells is actually controversial amongst HIV researchers because, though the idea of an HIV+ person having more T-cells seems like an excellent idea, many researchers feel that echinacea just creates more target cells to infect. Many are also concerned about animal studies showing that echinacea increases levels of "tumor necrosis factor alpha", a substance produced by the immune system to kill unhealthy cells. High levels of TNF-alpha have been linked to the progression of HIV disease.
It is also a mild anti-biotic and anti-fungal agent.