Astragalus
Astragalus membranaceus or milk vetch has been used in Chinese medicine for over 2,000 years to strengthen the immune and respiratory systems and to fight the flu. Astragalus belongs to a class of herbs called adaptogens, and helps the body handle stress. Astragalus also fights pathogens like bacteria and viruses.
Dosage: one dropper of tincture of Astragalus (standardized to 15 percent polysaccharides) to a hot liquid like tea or soup three times a day. As tablets, take 350 to 400 milligrams three times a day.