According to the University of Maryland’s Medical Center, if you are sensitive to daises, chrysanthemums, or ragweed, you may also experience an allergic reaction to burdock and people who are dehydrated should not take burdock because the herb’s diuretic effects may make dehydration worse. They also suggest to avoid taking burdock if you have been prescribed any diuretic or diabetic drugs.

Anaphylaxis due to ingestion of burdock.
– Int J Dermatol. 2003 Jun;42(6):472-3. — Anaphylaxis due to burdock. — Sasaki Y, Kimura Y, Tsunoda T, Tagami H.

Allergic reaction, including itching or hives from skin contact.

Burdock is not recommended for children less than two years old, or for women who are pregnant or breastfeeding. There are no scientific studies evaluating its safety in these situations.

Burdock can cause both high and low blood sugar in mice, so diabetic patients should be careful and monitor their blood sugar carefully when taking burdock.

Tinctures are not recommended for people with severe liver disease, because they contain alcohol.