Herb library · Herb · Juglans nigra
Black walnut hull
The green-to-black outer husk of the eastern black walnut, sold dried or as a tincture, mostly for intestinal worms. It stains skin brown and has a long folk history, but it has only been studied in the lab, never in people.
Traditional use
King's American Dispensatory recorded in the 1890s that the juice of the black walnut rind was said to be good for skin eruptions such as herpes and eczema, and that a decoction had been used to expel worms. Today the hull is sold mainly in "parasite cleanse" products, often mixed with wormwood and cloves.
What studies show
No studies in people of this herb on its own yet. What is known of it comes from the traditions that use it.
- Insufficient
Intestinal worms and skin: no studies in people were found. Hull and leaf extracts act on bacteria, fungi and cancer cells in lab dishes, which does not show what the hull does in a person or that it clears worms.
Be careful of
Cautions
- NoteKeep hulls, nuts and wood away from dogs and horses. In 65 dogs that ate black walnuts or hulls, vomiting was common; dogs that chewed the wood more often had nerve or muscle signs. Horses bedded on shavings of black walnut heartwood commonly develop laminitis, a painful hoof disease.
- ConditionWorms are diagnosed with a stool test and have proven medicines. A folk remedy is not a substitute for testing, especially in children.
- NoteFresh hulls stain skin, nails and clothing dark brown for days.
- PregnancyNo safety information for pregnancy or breastfeeding was found in the sources used here.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“The juice of the rind of black walnut is said to cure herpes, eczema, porrigo, etc., and a decoction has been used to remove worms.”
Sources
- Comprehensive characterization of phytochemical composition, membrane permeability, and antiproliferative activity of Juglans nigra polyphenols (Int J Mol Sci, 2024) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
- Clinical signs associated with ingestion of black walnut tree (Juglans nigra) wood, nuts, and hulls in dogs: 93 cases (J Am Vet Med Assoc, 2016) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
- Black walnut extract: an inflammatory model (review, 2010) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
Reviewed September 25, 2026.