Dandelion leaf and root should not be used by people with gallstones without the supervision of a healthcare practitioner.⁹ People with an obstruction of the bile ducts should not take dandelion.

Animal studies have shown that dandelion can lower blood sugar levels. In a case report, a patient who was taking insulin for diabetes developed episodes of hypoglycemia after adding dandelion to her treatment regimen.¹⁰ People taking blood sugar-lowering drugs should therefore not take dandelion without the supervision of a doctor.

In cases of stomach ulcer or gastritis, dandelion should be used cautiously, as it may cause overproduction of stomach acid. Those experiencing fluid or water retention should consult a doctor before taking dandelion leaves. The milky latex in the stem and leaves of fresh dandelion may cause an allergic rash in some people.

Dandelion root contains approximately 40% inulin,¹¹ a fiber widely distributed in fruits, vegetables and plants. Inulin is classified as a food ingredient (not as an additive) and is considered to be safe to eat.¹² In fact, inulin is a significant part of the daily diet of most of the world’s population.¹³ However, there is a report of a 39-year old man having a life-threatening allergic reaction after consuming high amounts of inulin from multiple sources.¹⁴ Allergy to inulin in this individual was confirmed by laboratory tests. Such sensitivities are exceedingly rare. Moreover, this man did not take dandelion. Nevertheless, people with a confirmed sensitivity to inulin should avoid dandelion.