Astragalus acts as a tonic to protect the immune system. It has been shown to increase intereferon and white blood cell counts both of which may shorten the duration of colds, flu and immune-deficiency related problems. We recommend Astragalus should be taken from the first day of Autumn until the first day of Spring. Caution: Should not be taken if fever is present. Astragalus also supports adrenal gland function making it very useful for stress.