University of Maryland article has a warning about possible interaction with antacids.
Antacids -- Dandelion may increase the amount of stomach acid, so antacids may not work as well.
This warning might be relevant to the Whipple patients. If you are a patient post-Whipple, increased stomach acidity is likely undesirable. Talk to your surgeon before adding dandelion to your diet.
The reason I mention this:
My wife had a Whipple in 07/2011. She takes Pantoloc (Pantoprazole) every morning to *reduce* stomach acidity. The surgeon prescribed it to protect the new surgical connection between the small intestine and the stomach. My understanding is she will be taking this medication for the rest of her life.
Sloan-Kettering article mentions another contraindication relevant to CC patients.
Patients with obstruction of the bile duct or gall bladder should not take dandelion.
The reason for this warning: dandelion raises the production of bile in the liver.