Several herbs interact dangerously with kava-kava, the Pacific medicinal herb used as a treatment for anxiety and insomnia. You should not use kava if you are taking any of the following herbs, because they can dangerous side effects when used in combination. Wait at least two weeks before using kava-kava if yuo have taken any of the following herbs.
There is one report of liver damage in a person who used passionflower and kava-kava together. Although passionflower, which has medicinal properties similar to kava, is safe when used alone, it may increase the risk of liver-damaging side effects associated with kava-kava.
Comfrey is rarely sold in the United States because it can cause severe liver damage when taken by mouth. This risk is especially great if you use other herbs that tax liver function, such as kava. Do not use kava if you have taken comfrey recently.
There is some concern that yohimbe, used to treat erectile dysfunction, can hurt the liver. In theory, yohimbe and kava can interact dangerously, leading to liver failure. Stay on the safe side and avoid this combination.
Valerian root has sedative and anxiolytic effects similar to kava. If you take the two herbs together, you might have an increased risk of severe sedation. This could cause central nervous system problems, extrme drowsiness and dangerously low blood pressure.
Chamomile is also an herbal sedative. If you use chamomile and kava-kava togehter, you may feel excessively drowsy or have difficulty waking up. It can also alter your blood pressure or lead to depression. Use this combination cautiously, if at all.
In aromatherapy, lavender oil is used as a sedative. Even when it is not taken by mouth, lavender can increase the risk of sedative side effects from kava. It’s best to stay on the safe side and avoid taking lavender with kava-kava.
Visit the National Institutes of Health or University of Maryland Medical Center for more information about kava-kava root.