I picked up the four herbs at the health food store and boiled them up a la Glum's instructions. I drank that for a few months until early in 1994 when I spotted the first ad from Essiac International. I immediately called the company and spoke with David Dobbie, a research scientist who had taken over the reins from Resperin and was making Essiac available as a shelf product with no therapeutic claims whatsoever. You have no idea what you are getting. The correct ratios are definitely important and we are the only people with the proportions specified directly by Rene Caisse.
Sheep sorrel is a case in point.
This is a critical ingredient and Mr. Dobbie said it is expensive and difficult to source in commercial quantities. So substitutes such as curly dock or yellow dock are widely used. Harvesting times are also important. For example indian rhubarb root must be six years old, while burdock root must be from first year plants. I have been able to confirm that Mr. Dobbie's information about sheep sorrel is accurate.