As the temperature drops, more Americans start to take echinacea to bolster their immune system. While studies on the supplement's efficacy show conflicting results, it's likely due to variation in the contents of product tests. One species in particular, Echinacea purpurea, works best.
Is it safe? Generally, yes. There's no harm in trying it unless you're allergic to ragweed, have an autoimmune disorder, or are taking drugs that can hurt the liver.