SuppleGut Take the quiz

Western herbalism

Black walnutJuglans nigra

Black walnut hull is sold as a parasite cleanse; we could find no human trial of it, and its juglone is toxic to cells in laboratory work.

Botanical name
Juglans nigra
Part used
green hull (outer husk of the nut); also leaf and bark
Also called
Black walnut hull, Eastern black walnut
Used in
Western herbalism
Taken for
Antimicrobial use
Sold as
tincture, capsules, powder, tea, extract

The plant

Black walnut is a large North American tree, Juglans nigra, of the walnut family (Juglandaceae). The supplement material is not the nut but the hull, the green outer husk that surrounds it, which stains hands and cloth dark brown. Leaf and bark are also used in herbal practice. The hull is sold as a liquid tincture or extract, as capsules of powdered hull and as a tea, and it is a standard ingredient in multi-herb parasite-cleanse formulas, often alongside wormwood and clove.

Two features of the hull matter for how it is read. It is rich in tannins, astringent compounds that bind proteins, and it contains juglone (5-hydroxy-1,4-naphthoquinone), a quinone that is toxic to cells in the laboratory. Juglone is the compound the Natural Medicines safety entry singles out.

How the traditions use it

Western herbalism

The Natural Medicines database lists the hull’s traditional uses as parasitic worm infections and certain other infections including diphtheria and syphilis, plus leukemia, gargles for the mouth and throat, skin wounds, and hair dye. It says the tannins can reduce pain and swelling and dry up body fluids, which is the astringent idea behind the gargle and wound uses. A laboratory paper on juglone notes that black walnut preparations have been used as hair dyes and skin colorants and applied to the skin for acne, inflammatory diseases, ringworm and fungal, bacterial or viral infections. The intestinal-worm use belongs to this Western folk-herbal tradition, and it is the origin of black walnut hull in the cleanse formulas.

What is in it

The hull contains tannins and the naphthoquinone juglone. In cultured skin cells, juglone and the related plant quinone plumbagin reduced cell viability in a concentration-dependent way at 1 to 20 micromolar, through redox cycling and by depleting glutathione, the cell’s own antioxidant. In mouse early embryos juglone arrested development through oxidative stress and DNA damage, and in animal work free juglone had a plasma half-life of about 2 hours and went rapidly to the kidneys, where it damaged tissue. These are laboratory and animal findings. They explain why juglone is studied as an anticancer agent and also why it is a safety concern.

What the human trials show

We could find no controlled study in people of black walnut hull for intestinal parasites, constipation or any other gut outcome. The Natural Medicines database rates the evidence as insufficient to rate for intestinal worms and for each of its other uses, and a PubMed search for black walnut hull and anthelmintic activity returned nothing.

The nearest antiparasitic data are not from black walnut and not from people. An ethanol extract of English walnut leaf (Juglans regia, a different species and a different part) at 100 mg/ml inhibited the movement of adult chicken roundworms (Ascaridia galli) by 96.5 percent at 24 hours in a dish, against 100 percent for the drug levamisole. In chickens given the extract, the largest effect was a 67.28 percent reduction in fecal egg count on day 14, and at 500 mg/kg there was no significant difference in worm counts from untreated birds. In a separate screen of 46 traditional plants as tinctures against two livestock nematode larvae, five plants showed nematocidal action and a walnut-family species was not among them.

What has not been tested: black walnut hull against any human intestinal parasite, stool-test outcomes after taking it, how much juglone a capsule or tincture contains and absorbs, and a dose that is both active and free of cell toxicity. Because the supplements are tannin-rich plant extracts, a test tube result does not tell us what reaches the gut lining in a person.

StudyDoseWhat it found
Natural Medicines database rating of black walnut hull (via RxList)No dose range establishedInsufficient evidence to rate for intestinal worms, leukemia, diphtheria, syphilis, gargles and skin wounds
Laboratory and chicken study of Juglans regia (English walnut) leaf extract against Ascaridia galli roundworm (different species, animal) PMID 38771447100 mg/ml in vitro; 500, 1000 and 2000 mg/kg in chickens96.5% inhibition of worm motility at 24 h in a dish; best fecal egg count reduction 67.28% on day 14; no significant worm-count difference at 500 mg/kg
Screen of 46 traditional plant tinctures against Strongyloides papillosus and Haemonchus contortus larvae (livestock nematodes) PMID 41463411In vitroFive plants showed nematocidal action; a Juglandaceae (walnut-family) species was not among them
Laboratory study of juglone and plumbagin cytotoxicity in HaCaT skin cells PMID 147279191 to 20 micromolar in vitroConcentration-dependent fall in cell viability through redox cycling and glutathione depletion
Study of juglone in early mouse embryos PMID 33010468In vitroJuglone lowered embryo development rate and caused oxidative stress, DNA damage and apoptosis; vitamin C partly protected

How much the studies and the texts used

No human trial gives a dose. The Natural Medicines database states there is not enough scientific information to determine an appropriate range of doses for black walnut. The preparations on sale are tinctures of the hull, capsules of powdered hull and teas, and labels differ in how much hull they contain. The only dosing instruction in the Natural Medicines entry is about timing: because the tannins can reduce the absorption of medicines taken by mouth, it advises taking black walnut at least one hour after oral medications. The chicken study of walnut leaf above used 500 to 2000 mg/kg of an ethanol extract, which is an animal dose and not one for people.

Doses here describe what studies and pharmacopoeias used. They are not a recommendation for any person; a clinician or pharmacist who knows your medicines and conditions is the right person to ask.

Side effects and cautions

The Natural Medicines database rates short-term oral use of the hull as possibly safe for most people and says what side effects short-term use might cause is unknown. It rates use on the skin possibly unsafe because juglone might cause tongue or lip cancer, especially if applied daily. For pregnancy and breastfeeding it says there is not enough reliable information on oral use and advises avoiding it, and it advises avoiding skin application as well. The laboratory findings that juglone is toxic to skin cells, harms early mouse embryos and damages the kidney in animals are not human safety data, and long-term human safety of regular hull supplements has not been studied.

Interactions

The main interaction is physical rather than metabolic. The Natural Medicines database rates black walnut moderate with oral medications in general, because the hull’s tannins can bind to drugs in the gut and reduce how much is absorbed, and advises taking it at least one hour after medicines taken by mouth. The site’s own drug rules apply that spacing to all oral medicines. We could find no study measuring black walnut’s effect on the blood level of a specific drug, so this rests on the tannin mechanism.

Black walnut on the shelf: the products that contain it

The products here name black walnut among their actives. How much of it a serving holds, and whether that matches any trial, is on each page.

NOW Foods Green Black Walnut Wormwood Complex 4.4 out of 5 from 4,921 ratings from Amazon · ~$0.48 a day at the full label dose, about $0.12 at the lowest Renew Life PARA SMART Cleansing Formula, 15-Day Program 4.2 out of 5 from 1,398 ratings from Amazon · ~$2.04 a day across the full 15-day program Biocidin Botanicals Biocidin Broad-Spectrum Liquid Formula 4.5 out of 5 from 1,079 ratings from Amazon · ~$1.41 per day at the full 15-drop dose Organics Ocean Better Fiber with Psyllium Husk and Slippery Elm 4.4 out of 5 from 726 ratings from Amazon · $1.20 a day

From the herb to a product that fits you

Three minutes, no sign-up: the quiz turns your symptoms and routine into one named product and says why.

Take the quiz

Often paired or compared

Western Wormwood Artemisia absinthium Ayurvedic / TCM / Western Clove Syzygium aromaticum Western Pau d'arco Tabebuia impetiginosa (Handroanthus impetiginosus) Western Quassia Quassia amara; Picrasma excelsa Western Cat's claw Uncaria tomentosa

What people want to know

Does black walnut hull kill intestinal parasites?

We could find no study of black walnut hull in people with intestinal parasites, and the Natural Medicines database rates the evidence for intestinal worms as insufficient to rate. The nearest data are an English walnut leaf extract tested on chicken roundworms and a screen of 46 plant tinctures against livestock nematode larvae, in which a walnut-family species did not show nematocidal action.

What is juglone?

Juglone is a naphthoquinone made by black walnut trees and present in the hull. In laboratory work it reduces the viability of skin cells at 1 to 20 micromolar, harms early mouse embryos and damages the kidney in animals. Natural Medicines notes it might cause tongue or lip cancer if applied to the skin daily.

When should black walnut be taken relative to medicines?

The Natural Medicines database says the hull’s tannins can reduce how much of an oral medicine is absorbed, and advises taking black walnut at least one hour after oral medications. The site’s own interaction rules use the same one-hour spacing.

Is black walnut hull safe in pregnancy?

The Natural Medicines database says there is not enough reliable information on oral use in pregnancy and breastfeeding and advises avoiding it. Juglone harmed early embryo development in a mouse study, which is a laboratory finding.

Is the hull the same as the nut?

No. The supplement material is the green outer hull, which holds the juglone and tannins. Natural Medicines’ safety discussion covers the hull only and does not address the nut itself.

Sources