Hulda Regher Clark

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Black Walnut Hull

The History and Use of the Black Walnut Hull in Alternative Medicine


 Several species of walnut trees grow in the United States. Two of these are native to the East – the black walnut and the butternut, also called the white walnut. Black walnut trees grow in forests from Massachusetts to Florida and west to Texas. They are hardy trees that are grown mainly for their lumber. The nuts also are harvested and sold. They have a distinctive and rich flavor, but their shell is hard and thick.

Black walnut wood is dark purplish-brown, with a fine grain and luster. It is valuable for interior finishing, furniture, and gunstocks. This wood is becoming rare.

The Black Walnut Hull contains a number of active ingredients, of which the most important are juglone, tannins and iodine.

Juglone is a brown constituent of the black walnut hull, leafs, bark and even roots. It is called a phytotoxic allelochemical. Phytotoxic means that it kills plants, and allelochemical means that the black walnut tree produces this chemical to keep other plants from growing around it. You may have noticed that vegetation under black walnut trees is rather scarce, and this is the reason. Since yeast and fungus in humans are also plants, it has been conjectured that it will work against fungus as well and it has been described as an anti-fungal in many herbal reference books. There is some scientific evidence also. Whether juglone works against parasitic infections is matter of scientific discussion. However, the NIH (National Institute of Health) writes: “Crushed unripe walnut hulls have been used for generations in various types of folk medicine […] to treat fungal, bacterial or viral infections such as herpes or warts. External applications of walnut also kill ringworm, and Chinese herbalists use this substance to kill tapeworm.” 

Since we suspect that juglone is the most important ingredient in black walnut hull tincture; and since it can quickly oxidize whereby the tincture becomes less potent, we have developed a laboratory method to monitor the concentration of juglone in our black walnut hull tincture.


Tannins act as a defense mechanism in plants against pathogens, herbivores and hostile environmental conditions. The antihelminthic properties of tannins have been shown in scientific studies. Tannins are described to be antibacterial, anticancer, antidiarrheic, antihepatotoxic, chelator, antihypertensive, antitumor, cancer preventive, antiulcer. Unfortunately, little scientific information can be found about it.

Iodine is widely used as an antiseptic in medicine. It works by attaching itself to the pathogenic bacteria and thereby killing them. Dr. Clark frequently recommends the use of Lugol’s iodine for antiseptic purposes. 

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