Now is the season to maintain a healthy immune system and build a protocol to prevent cold and flu.  My favorite three herbs for preventing a cold or the flu are pelargonium, andrographis, and echinacea.  Clinical studies support the use of these three herbs to reduce the severity and duration of a cold and flu.  With the season, bronchitis is a common occurrence.  For any upper respiratory tract inflammation and infection, my favorite three herbs are boswellia, ivy, and thyme.  For sinuses, oil of eucalyptus and oil of myrtle, taken together, prevent sinus congestion and headache.  Nasal passages remain wide open with no difficulty breathing.  We cannot leave out vitamin D3 as vitamin D3 also supports immune function.  And, in a recent study, it reduces the risk of influenza by 64.5%.  A flu shot reduces the risk about 65%.  Vitamin D and the flu shot are almost exactly equal in effectiveness.   In other studies conducted by Dr. Michael Holick and Dr. Hector De Luca, it was reported that vitamin D3 reduces the risk of influenza by 90%.  All of these recommendations are without side effects, a huge benefit when you consider that all drugs have side effects.  All drugs are poison and all drugs have the potential of causing cancer, and in many cases, death.