A thousand years ago, the Incas of Peru found the inner bark of the pink-flowered lapacho tree indispensable for treating fever, sore throat, dysentery, snakebite, bladder and yeast infections, and even cancer. They also used its wood to make bows for hunting.

Although preliminary lab tests show that a chemical in pau d’arco called lapachol can kill some viruses, bacteria, and fungi in test tubes, it isn’t known whether it will have the same effects when taken by humans. So even though pau d’arco is sometimes used for conditions ranging from candidiasis (a yeast infection of the vaginal or oral areas), herpes simplex virus, and influenza to parasitic diseases such as schistosomiasis and bacterial infections such as brucellosis, there is no evidence it works. Test tube studies to evaluate whether pau d’arco has any effect on cancer have shown mixed results; and even in studies where pau d’arco does reduce the number of cancer cells, the amounts used would be toxic to humans.

The same is also true of some of the doses that might be needed to kill bacteria or viruses. If you decide to take pau d’arco, do so only under your doctor’s supervision.

First, the research isolated the chemical lapachol in pau d’arco that they felt cured the cancer. Since then Researchers have isolated over 20 active chemicals in pau d’arco. Some feel it is a combination of several or all these together that makes it effective. Second, it has been shown that the use of the whole herb does not create the side effects that extracted lapachol causes.

Pau d’arco has certain anti-inflammatory and anti-viral activity, including against herpes I and II. It may reduce viral replication, according to a report in the Proceedings of the National Academy of Sciences.

Pau d’arco is sold as tablets, dried bark tea, and tincture (which contains alcohol). The chemicals that give pau d’arco its medicinal effects dissolve poorly in water, so a tea is not recommended.

Tea can be made from the bark by adding one tbsp of bark for every three cups of water. The tea should be boiled for twenty minutes or longer in a non-aluminum pot. One cup of tea can be taken three or four times daily for acute conditions. One-half cup three or four times daily is recommended for other conditions. Pau d’arco tea has a cool, bitter flavor.

Dosage In tablets or capsules, 1 to 4 grams per day in divided doses–or 1 to 2 teaspoons of tincture three times a day. Consuming 1.5 grams per day or more may cause dizziness and GI upset, so consult your herbalist. Avoid pau d’arco if you’re taking anticoagulants or having surgery, or if you are pregnant or nursing.