Drinking chamomile tea can cause drowsiness, and if taken in large doses, vomiting, according to WebMD. Chamomile tea may trigger an allergic reaction in people who have allergies to plants in the daisy family.
Because chamomile contains a small amount of coumarin, which has mild blood-thinning effects, people should check with their doctors if they have any health problems before consuming it. There are also concerns about possible interactions with anesthetic drugs, so those with scheduled surgeries should not ingest it during the two weeks leading up to their procedures. Additionally, women who are pregnant or breastfeeding should not consume chamomile, reports WebMD.