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Lapacho is a name for the herb Tabebuia avellanedae, more commonly called pau d'arco and taheebo. It is promoted as useful for treating a variety of health problems and illnesses, including cancer; however, no scientific evidence verifies that it works, according to the University of Maryland Medical Center. Side effects are unlikely at recommended doses, but some serious harmful effects are associated with high doses. Taking lapacho or any other herbs should only be done with the supervision of a qualified healthcare practitioner.

Common Effects

Even low doses of lapacho can cause gastrointestinal side effects of nausea, vomiting and diarrhea, according to the American Cancer society. Dizziness and urine discoloration are other reported side effects.


Lapacho has blood-thinning effects and slows clotting. This can increase the risk of uncontrolled bleeding. Doses that might be useful for treating tumors would present a serious bleeding risk, explains the American Cancer Society. The Society says research stalled once this effect was discovered, and Canada has banned the substance. The risk is particularly dangerous for people with hemophilia or other bleeding disorders, or those who take medications with blood-thinning properties. Some of these medications include warfarin, heparin, aspirin, naproxen and ibuprofen.

Allergic Reaction and Asthma

An allergic reaction to lapacho is possible. In addition, some people have experienced asthma when working in settings where they were exposed to wood dust of this plant, notes the American Cancer Society.


Active components in lapacho bark called naphthaquinones have anti-cancer properties, but this is because the chemicals are toxic, according to the University of California at San Diego Moores Cancer Center. The poisonous chemicals kill cancer cells in the laboratory, but the amount of lapacho a human has to take for the same effect is too toxic. Taking large doses may cause liver and kidney damage.

Pregnancy and Breastfeeding Dangers

Research with pregnant animals has found lapacho to be associated with birth defects and fetal death, according to the American Cancer Society. The anti-cancer properties affect rapidly dividing cells, including those in a fetus. Pregnant women thus should not take lapacho, and to be on the safe side, breastfeeding women should not take it either.