North American folk remedy with a single regulatory-approved use: traditional vermifuge (worm expulsion). Zero human trials exist. The primary compound, juglone, is mutagenic in lab assays. Short-term use only — 14 days maximum without practitioner oversight.
Traditions: North American Indigenous, Eclectic Medicine, American folk herbalism
Green hull preparations for intestinal worm expulsion, skin parasites (scabies), ringworm, and wound cleansing. Fresh hull juice applied topically for tinea and eczema. Bark decoctions as gargles for mouth sores and gum disease.
Adopted anthelmintic use from Indigenous practice. Also applied to chronic skin diseases (herpetic eruptions, impetigo, favus, ringworm) and used as an 'alterative' (blood purifier) for syphilis and scrofula before antibiotics. Hull extracts macerated in dilute alcohol.
Hull tinctures for Candida overgrowth and 'parasite cleanses.' Often combined with wormwood and cloves in protocols popularized in the 1990s. Topical tincture for athlete's foot and nail fungus remains common in folk herbalism.
No human RCTs exist for any therapeutic use of black walnut. The only regulatory recognition worldwide is Health Canada's 2022 traditional use claim for anthelmintic/vermifuge use — a traditional-use designation that required no clinical trial evidence. All pharmacological data is in vitro: juglone kills cells, inhibits bacteria and fungi in culture, and triggers ferroptosis in pancreatic cancer cells. Whether any of this translates to useful effects in humans is an open question.
Anthelmintic/vermifuge claim approved for adults 18+. Dose: 0.65–2.75 g/day unripe hull. Maximum 14 days self-directed. Evidence basis: traditional use only — no clinical trials submitted or required.
Juglone IC50 in mouse fibroblasts: 60 μmol/L at 48h. Ames test positive (mutagenic) with metabolic activation at 1.25–2.5 μmol/L. Nano-encapsulated form eliminated mutagenicity in the same assay.
161 compounds identified across hull, bark, and leaf. Juglone showed positive GI membrane permeability and blood-brain-barrier penetration potential by PAMPA. Antiproliferative activity against three human tumor cell lines comparable to reference compounds — in vitro only.
Jug n 4 (11S globulin) bound IgE in 32% of 25 DBPCFC-confirmed walnut allergy patients. Establishes clinical cross-reactivity between J. nigra and J. regia (English walnut).
The only regulatory-approved form (Health Canada). Commercial capsules typically 250–500 mg — that's 2–5 capsules per day. Hard 14-day cap for self-directed use.
Aligns with Health Canada dose range at the 1:2 ratio. Ethanolic extraction preserves juglone better than water alone. Naturopathic tradition; 14-day limit applies.
Very low hull equivalent per dose. 2 weeks on / 2 weeks off cycling convention. Practitioner-supervised use in some jurisdictions.
Most potent commercially available form — fresh extraction preserves reduced juglone before oxidative blackening. Practitioner use only.
For skin fungal conditions (athlete's foot, ringworm, nail fungus). Brown-black staining is unavoidable. Nitrile gloves required when handling fresh hull.
Black walnut sits at an unusual position in herbal medicine: no human clinical trials exist for any therapeutic use, yet it holds a regulatory-approved traditional use claim in Canada. That distinction matters.
Health Canada’s 2022 NHPID monograph approved black walnut hull as a traditional vermifuge — to help expel intestinal worms. This wasn’t based on clinical trials; traditional use designations don’t require them. It’s regulatory recognition that the tradition is real and plausible, not proof that it works. No other regulatory body worldwide (not WHO, Commission E, EMA, or USP) has issued a monograph for Juglans nigra.
What lab work shows:
The critical caveat: none of this has been tested in humans. We don’t know what plasma concentrations of juglone are achievable after oral dosing. We don’t know if the anthelmintic, antifungal, or any other effect observed in the lab translates to a useful clinical outcome.
The safety signal you need to know: juglone is Ames-positive — mutagenic in a standard bacterial assay — when metabolically activated by CYP450 enzymes, at concentrations of 1.25–2.5 μmol/L [2]. This is the scientific basis for the universal 14-day use limit. We don’t know whether therapeutic oral doses produce mutagenic juglone concentrations in human tissue. We don’t have human pharmacokinetic data. The risk is theoretical but real enough that caution is the only defensible position.
Black walnut’s traditional record is North American and concentrated — not the multi-thousand-year, multi-civilization story you get with some Ayurvedic herbs. Its depth is regional and genuine.
Indigenous North America: The anthelmintic use is the most consistent thread across pre-contact and 19th-century Indigenous traditions. Unripe green hulls were prepared as teas or infusions to expel roundworms, tapeworms, and pinworms. The timing of harvest — green hulls in early autumn — aligned with what practitioners called the “wormy season.” Fresh hull juice was applied topically for ringworm and skin parasites; bark decoctions served as antiseptic gargles.
Eclectic Physicians (1820s–1930s): The 19th-century American Eclectic school adopted and systematized these uses. Black walnut appeared in their materia medica for intestinal worms, skin diseases (impetigo, herpetic eruptions, favus), and as an “alterative” — a category roughly equivalent to “blood purifier” — for syphilis and scrofula, reflecting pre-antibiotic practice. Their preparation of choice was green hull extract in dilute alcohol, often combined with other alteratives like yellow dock and sarsaparilla.
20th-century folk herbalism: The tradition continued and narrowed toward Candida overgrowth and “parasite cleansing,” particularly after Hulda Clark’s 1990s protocols popularized black walnut alongside wormwood and cloves. There’s no clinical evidence for these combination protocols. The topical use for athlete’s foot and nail fungus persists in folk practice based on juglone’s documented antifungal activity in vitro.
The single traditional use that earned regulatory recognition — anthelmintic — is also the most historically consistent one, documented independently across Indigenous practice, Eclectic medicine, and folk herbalism.
Everything centers on the unripe green hull (pericarp) — not the nut, not the leaves, not the bark for internal use. Ripe, blackened hulls have substantially less juglone.
Dried hull powder or capsules (most accessible):
Liquid extract 1:2 (naturopathic standard):
Tincture 1:4 at 25% ethanol (traditional folk form):
Don’t make a strong tea or decoction for internal use at traditional bark-decoction ratios — those traditional preparations were often topical or intended for very short-term use, and the doses can far exceed the Health Canada safety threshold. Aqueous preparations also have poor juglone bioavailability since juglone is relatively insoluble in water and degrades in gastric acid.
Before starting:
During the 14 days:
For anthelmintic use:
For skin/topical use:
Stop immediately if:
What they typically report: GI activity (sometimes dramatic — this is expected with anthelmintic herbs), stool changes, and with topical use, clearing of fungal patches over 2–3 weeks.
Juglone is the same compound that makes walnut husks permanently stain everything they touch — wood, concrete, skin, teeth. If you’re using liquid preparations, expect brown-black discoloration of your lips, mouth, and teeth during use. Urine and stools typically darken. This is cosmetically annoying but not a health concern.
If you ever handle fresh green hulls directly: use nitrile gloves. Juglone penetrates latex, and the fresh-hull stain on skin takes weeks to fade. Outdoor processing is recommended — the allelopathic juice will kill nearby plants.
The problem unique to black walnut: no standardization exists anywhere. The primary active compound (juglone) is chemically unstable — it oxidizes during processing, drying, and storage, which is why Health Canada explicitly requires only “non-standardized” extracts. No pharmacopoeial monograph exists to verify against. The quality range across commercial products is wide and largely unverifiable.
What to look for:
Avoid: products that specify just “walnut hull” without indicating ripeness state, and any preparation claiming standardized juglone content — the instability of juglone makes this claim dubious or the product potentially unsafe.
Because no regulatory standard exists beyond Health Canada’s traditional use designation, the manufacturer’s quality controls are your only safeguard.
Black walnut hull is a genuine North American folk medicine with real phytochemistry and a consistent traditional use record for intestinal parasites. It also has zero human clinical trials, a mutagenic primary compound, a hard 14-day use limit, and significant drug interaction concerns.
What it might do: expel intestinal worms and help with topical fungal conditions — both plausible based on juglone’s in vitro activity and centuries of traditional use.
What it won’t do: serve as a long-term supplement, treat systemic Candida with certainty, or substitute for evidence-based treatments where those are available and appropriate.
The honest position: if you have a legitimate anthelmintic need, black walnut hull is the only herb with any regulatory recognition for that purpose, however modest. Use it at the approved dose, for the approved duration, with full respect for the contraindications and the drug interaction risk. Then stop.
For anything beyond that narrow traditional use, the evidence hasn’t arrived yet.
Duration: 14 days maximum for self-directed use. With a qualified practitioner, some sources support up to 6 weeks with 2 weeks on / 2 weeks off cycling.
What to notice:
Start at the low end: 0.65 g/day powder (one 500 mg capsule) or 5 drops of tincture once daily. Always take with food — never on an empty stomach. Keep a 1–2 hour gap from any other medications in either direction. Stop at 14 days regardless of outcome. If you're experiencing significant GI distress at any point, reduce dose or stop.
Generally considered: caution
Contraindications:
Pregnancy/Nursing: Contraindicated in both pregnancy and lactation. Juglone mutagenicity raises theoretical teratogenic risk. Traditional sources in some cases record high-dose hull preparations as abortifacient — do not use.
Drug interaction you cannot ignore: the hull contains approximately 45% tannins, which bind oral medications and reduce their absorption. Separate all oral medications from black walnut preparations by at least 1 hour — preferably 2 hours. This matters for antibiotics (especially tetracyclines and fluoroquinolones), iron supplements, digoxin, antipsychotics, antidepressants, and most other orally-administered drugs. CYP450 interactions are theoretically possible (juglone requires CYP activation to become mutagenic) but uncharacterized in humans. Darkening of stool and urine is normal and expected. Contact dermatitis from hull handling is documented occupationally — if you develop a rash from topical use, stop.