What are butterbur’s main drawbacks?

Common side effects of butterbur include burping, stomach upset, and headache, as well as allergic reactions, including itchy eyes and wheezing. People with allergies to ragweed and daisies (common causes of seasonal allergic rhinitis) may have allergic cross-reactivity to butterbur. Butterbur contains pyrrolizidine alkaloids, which are known to be toxic to the liver, and there have been rare reports of liver toxicity with butterbur use.^[1][2]