Echinacea, obtained from the roots of several species of that genus, is a natural antibiotic and immune-system enhancer from the Native American herbal tradition. Echinacea is familiar to gardeners as purple cone flower, an ornamental plant. It grows wild throughout the plains of North America and is now extensively cultivated as a medicinal. Practitioners of natural medicine in Europe and America have long valued it. In recent years research, done mostly in Germany, has confirmed its antiviral, antibacterial, and immunity-enhancing properties. You can buy tinctures, capsules, tablets, and extracts of echinacea in all health food and herb stores. The root produces a curious and distinctive numbing sensation when held in the mouth for a few minutes. If a commercial preparation does not do this, it is not good. Always test echinacea products by putting a bit on the tongue; return any that fail to cause numbness. Try echinacea as a first line of treatment for common infections before resorting to conventional antibiotics. Use it for colds, flu, sore throats, and episodes of low resistance. A dropperful of tincture in water four times a day or two capsules of freeze-dried extract four times a day is the dose for adults; give children under 10 half those amounts. To build immunity in the absence of infection, halve the adult dose and stay on the remedy for two weeks at a time. Echinacea loses its efficacy when taken continually; it is better to take it for two weeks at a time, alternating with two weeks off.