Herbal Iron Formula by Dr. Christopher 100 Capsule Yellow Dock Combination Ingredients White Oak Bark Mullein Herb Yellow DockRoot Black Walnut Comfrey Root Lobelia and Marshmallow Root.Labeled for external use due to comfrey . The herb Yellow Dock has considerable amounts of vitamin C whichhas been used historically to help with the absorption of Iron.Yellow Dock is also over 50 iron by weight thus it has been used historically for iron deficiency.