SAMBUCOL® Immune System is based on the world-renowned SAMBUCOL® herbal remedy people have used for decades to help increase their resistance to colds, flu, and other illnesses. SAMBUCOL® Immune System also includes echinacea, zinc and vitamin C for additional immune system support. Sambucol's name is derived from one of its principal ingredients, black elderberry or Sambucus nigra L.. Black elderberry extract became been the subject of clinical studies after noted virologist Madeleine Mumcuoglu, Ph.D. developed a proprietary method for black elderberry extraction while working on her doctoral thesis. SAMBUCOL® Immune System contains the proprietary black elderberry extract in a gluten free base.