Sassafras can cause vomiting, diarrhea, nausea and abdominal pain. The oil also will burn the skin. The amount needed to bring about these reactions varies according to the individual.
Changes in breathing patterns, such as becoming too rapid or too shallow, can occur in high doses. Users also can experience dizziness, hallucinations and unconsciousness. Kidney damage can result and it will take months to recover. Be advised that biological changes from toxic levels of sassafras also can cause death.
Researchers do not know how much sassafras needs to be consumed by humans in order to cause cancer but the Food and Drug Administration has discovered that sassafras causes cancer in rats. One cup of sassafras contains at least 200 mg of safrole and that is four times the amount considered hazardous.