Author: Marie Collison, Class of ‘25
Chamomile is a plant that is widely used in herbal medicine for a wide variety of reasons. It has been reported to have anti-inflammatory, antioxidant, anticarcinogenic, antidepressive, and sedative properties. Despite these benefits, current medical recommendations list chamomile as a substance that should not be ingested prior to surgery due to fears that it may increase the risk of bleeding. However, these protocols rest on a singular case study from 2006 that proposed that compounds in chamomile interact with warfarin (an anticoagulant prescribed to preoperative patients), leading to a major risk of spontaneous hemorrhaging.
Research published in 2023 by Reona Kimura and Jonathon A. Schwartz of the Stony Brook Department of Anesthesiology investigated possible anticoagulant effects of chamomile intake in a preliminary, randomized trial study. They took eight volunteers of average health and provided two interventions: chamomile tea and a capsule of chamomile extract. To prevent overlap, the researchers had participants come in on two different days, with at least three days between visits. Blood samples were taken prior to treatments as a baseline and experimental samples were taken two hours and four hours post-ingestion. Blood clotting was measured in terms of the prothrombin time (PT), a measure of how long it takes for blood to clot. Kimura and Schwartz found that ingestion of chamomile tea increased the maximum PT by 0.7 seconds from baseline, which was a statistically significant change. The average percent increase, however, was only 5.5%, which did not meet their prespecified clinically relevant threshold of 10%. In contrast, chamomile capsules only prolonged the maximum PT value by 0.3 seconds which was neither statistically significant nor clinically relevant.
Although the initial 2006 case study may implicate chamomile as an anticoagulant that can increase the risk of hemorrhaging, many confounding factors were not investigated in follow-up studies. As such, the current protocols, while erring on the side of caution, are not scientifically founded. This study indicates that chamomile can in fact increase anticoagulation for a short period of time post-ingestion. However, their results are not deemed clinically significant by their pre-designated threshold, calling for further study of the potential clinical implications of their findings.
Figure 1 : Cup of chamomile tea
[1] Kimura, R., Schwartz, J. B., Romeiser, J., Senzel, L., Galanakis, D. K., Halper, D., & Bennett‐Guerrero, E. (2024). The acute effect of chamomile intake on blood coagulation tests in healthy volunteers: a randomized trial. The Journal of Applied Laboratory Medicine. https://doi.org/10.1093/jalm/jfad120
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