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(Walnut family)


Fifty species in seven genera are native to North temperate and sub-tropical regions, south to India, IndoChina and the Andes.

[Summary yet to be added]

Carya Nutt.

25 species are native to eastern North America. The trees (hickory) are cultivated for their wood and for the edible fruit e.g. pecans. Some species yield juglone (Thomson 1971).

Carya illinoinensis K.Koch
[syns Carya pecan Engl. & Graebner, Hicoria pecan Britton, Juglans illinoinensis Wangenh.]

Contact dermatitis occurring in a nut merchant from oil of pecan was briefly noted by Swinny (1951).

The pollen of pecan (Carya pecan) and other Carya spp. can cause hayfever (Wodehouse 1971).

Juglans L.

Fifteen species are native to the Mediterranean regions, eastern Asia, IndoChina and the Andes. Many species are cultivated for their fruit. The wood is valuable. The seeds yield oil.

A naphthaquinone, juglone, derived from J. regia, J. nigra, J. cinerea (butternut) and from some other plants of this family is present in the green parts as a glycoside or in reduced form and has been identified in water run-off from the trees (Thomson 1971).

The pollen of some species is suspected of causing hayfever (Wodehouse 1971).

Juglans hindsii Jepson ex R.E.Sm.
[syn. Juglans californica S.Watson var. hindsii Jepson]
Northern California Walnut

[Information available but not yet included in database]

Juglans nigra L.
[syn. Wallia nigra Alef.]
Black Walnut, American Walnut

The juice of the nut shells stains the skin dark brown. Schwartz (1931) stated that occupational dermatitis from this source was not known to occur. A single case of dermatitis of the finger-webs from occupational exposure was of irritant nature (Siegel 1954).

Juglans regia L.
European Walnut, English Walnut

This west Asian tree is widely cultivated and naturalized. Oil of Walnut is used for varnish, paint and perfumery (Greenberg and Lester 1954).

In traditional Chinese medicine, the oil from walnut seeds (nuts) is used as an application to several kinds of skin diseases, including eczema, chancre, and favus. The oil may also be applied to the hair as a pomade. A dye obtained from the pericarp of the fruit or from the bark or root of the tree may also be used to darken the hair. Juglans sieboldiana Maxim. is similarly used and not distinguished from Juglans regia in its medicinal uses (Stuart 1911). In NW Moroccan traditional medicine, an infusion of the leaf is taken orally for eczema, cutaneous infections and rheumatism; and the dried root bark is used externally for tooth care and gingivitis (Merzouki et al. 2000).

Contact-sensitivity to the wood was observed in five cases (Schürkämper 1972) and a case of contact dermatitis was reported by Schleicher (1974). A cabinet-maker who had extensive dermatitis showed a positive patch test reaction to walnut. He also showed positive patch test reactions to other woods, viz. teak (Tectona grandis L.f., fam. Labiatae) and Turreanthus and to other plants and allergens so that the significance of the positive reaction to walnut was considered doubtful. This patient has been receiving treatment for three years by systemic steroid administration for his illness which was considered to be polyarteritis with pulmonary involvement. He changed his occupation and made a complete recovery from the dermatitis (Calnan 1970, Woods and Calnan 1976). It seems possible that this case was an instance of occupational skin and lung wood toxicity or allergy.

The leaves, wood, bark and nut shells yield juglone, a naphthoquinone. According to Telegina (1965), juglone (5-oxy-1,4-naphthoquinone) is not irritant or sensitising. However, irritancy of juglone was reported by Auyone et al. (1968); and contact senstiivity to juglone was reported by Barniske (1957). Attempts to use juglone as a topical sunscreen were abandoned because commerically available juglone was found to yield a chromatographic fraction capable of causing allergic contact dermatitis; this fraction was unstable under ordinary conditions of storage (Runge 1972). Juglone was found to be a strong sensitiser for guinea pigs (Hausen 1974). Cross-sensitivity to quinones was reviewed by Mitchell (1975).

Ingestion of English walnuts has been correlated with recurrent oral ulceration (Editorial 1974).


  • Auyone, T.K., Deboer, B. and Oberpriller, J.0. (1968). Effects of intradermal injection of juglone in the guinea pig. Arch. Int. Pharmacodyn. 176: 298.
  • Barniske, R. (1957) Dermatitis bullosa, ausgelöst durch den Saftgrüner Walnutschalen (Juglans regia L.). Derm. Wochenschr. 135: 189.
  • Calnan, C.D. (1970) Avodiré wood sensitivity. Contact Dermatitis Newsletter (8), 190.
  • Editorial (1974) Recurrent oral ulceration. Br. Med. J. 2: 757.
  • Hausen, B.M. (1974) Pers. comm.
  • Merzouki A, Ed-derfoufi F, Molero Mesa J (2000) Contribution to the knowledge of Rifian traditional medicine. II: Folk medicine in Ksar Lakbir district (NW Morocco). Fitoterapia 71(3): 278-307 [doi] [url] [pmid]
  • Mitchell, J.C. (1975) Biochemical basis of geographic ecology. International Journal of Dermatology Part 1, 14: 239; Part 2, 14: 301.
  • Runge, W. (1972) Pers. comm.
  • Schleicher, H. (1974) Uber phytogene allergische Kontaktekzeme. Derm. Monatsschrift. 160: 433.
  • Schürkämper, H. (1972) Allergie durch tropische Hölzer. Thesis, Munich cited by Hausen, B.M. (1974) pers. comm.
  • Schwartz, L. (1931) Dermatitis venenata due to contact with Brazilian walnut. Publ. Health. Rep. 46: 1938.
  • Siegel JM (1954) Dermatitis due to black walnut juice. AMA Archives of Dermatology and Syphilology 70(4): 511-513 [doi] [url] [pmid]
  • Stuart GA (1911) Chinese Materia Medica. Vegetable Kingdom. Extensively revised from Dr. F. Porter Smith's work. Shanghai: American Presbyterian Mission Press [doi] [WorldCat] [url] [url-2]
  • Swinny, G. (1951) Periorbital dermatitis. Ann. Allergy 9:774.
  • Telegina, K.A. (1965) The use of Yuglon in treatment of neurodermatitis. Sov. Med. 28: 110.
  • Thomson RH (1971) Naturally Occurring Quinones, 2nd edn. London: Academic Press [doi] [WorldCat] [url]
  • Wodehouse, R.P. (1971) Hayfever Plants 2nd rev. edition. New York, Hafner.
  • Woods B, Calnan CD (1976) Toxic woods. British Journal of Dermatology 95(Suppl 13): 1-97 [doi] [url] [url-2] [pmid]

Richard J. Schmidt

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