Kathleen:  Of  Echinacea, senna, goldenseal, comfrey and licorice, echinacea
is the LEAST likely to cause problems!  Senna and licorice can cause
diarrhea and dehydration, whereas goldenseal and comfrey can be toxic in
moderate doses because of the way the liver metabolizes them (and immature
livers are more susceptible).  One should not continuously take echinacea on
a continuous basis.
Chris