Rhus Toxicodendron (U. S. P.)—Rhus Toxicodendron.

Fig. 209. Rhus toxicodendron. Photo: Toxicodendron radicans 3. Preparations: Tincture of Poison Oak
Related entries: Rhus Glabra (U. S. P.)—Rhus Glabra - Rhus Aromatica.—Fragrant Sumach

The fresh leaves of Rhus radicans, Linné (Rhus Toxicodendron, Linné).
Nat. Ord.—Anacardieae.
COMMON NAMES: Poison ivy, Poison oak, Poison wine.
ILLUSTRATION: Johnson, Medical Botany of North America, Fig. 117.

Botanical Source.Rhus Toxicodendron, or Poison oak, is a creeping shrub from 1 to 3 feet high, with long cord-like shoots, emitting strong lateral fibers; the stems are either erect or decumbent. The bark is brownish-gray. The leaves are ternate, on long, semi-cylindrical petioles; the leaflets are broadly oval or rhomboidal, 2 to 6 inches long, 2/3 as wide, petiolate, acuminate, smooth and shining above, slightly downy beneath, especially on the veins; the margin is sometimes entire, and sometimes variously toothed and lobed, in the same plant. The flowers are small, greenish-white, dioecious, and grow in axillary, subsessile, racemose panicles on the sides of the new shoots. Barren flowers have a calyx of 5 erect, acute segments, and a corolla of 5 oblong recurved petals; stamens erect with oblong anthers; in the center is a rudiment of a style. Fertile flowers about half the size of the preceding, with calyx and corolla similar, but more erect. They have 5 small abortive stamens, and a roundish ovary, crowned by a short, erect style bearing 3 small capitate stigmas. The fruit is a roundish, smooth, dry berry, of a pale-green color, approaching to white, and contains a solitary bony seed (L.—W.—G.).

History.Rhus radicans, or Poison ivy, and sometimes called Poison vine, is considered by botanists to be merely a variety of the above species; it has a climbing stem from 3 to 20 or more feet in length, and climbs trees, fences and neighboring objects, to which it becomes attached by its myriads of radiating tendrils. The leaflets are quite entire, smooth and shining on each side, with the exception of the veins beneath. These plants grow throughout the United States and Canada along fence-rows, in thickets, etc., flowering from May to August. They yield an abundance of yellowish narcotic acrid milky juice, which becomes black when exposed to the air, and forms an indelible ink when applied to linen; it is soluble in ether. The genus Rhus belongs to an interesting family of plants—the Anacardieae (Anacardiaceae) or Cashew family, a group of frequent occurrence in the tropical sections of both the eastern and western worlds, diminishing in distribution, however, as we approach the northern and southern sections of the temperate zones. Species of this family produce some of the most valued of tropical fruits, yet the group is chiefly distinguished for its gum-resinous juices, that from the majority of the species being caustic, becoming black on exposure to the air, and charged with an acrid, poisonous principle. This family includes not only the species of Rhus but also the plants yielding the Pistachia nut (Pistachia vera), Cashew-nut (Anacardium occidentale), Marking fruit or Oriental cashew-nut (Semecarpus Anacardium), Mango (Mangifera indica), the Mastich tree (Pistachia Lentiscus) and other products interesting from a medicinal or economic standpoint. As before intimated, several species of Rhus have been used in medicine and in the arts. Many of these are now obsolete as medicines. However, a brief enumeration of them and their chief characteristics and uses may not be out of place. The bark of the Wild olive or Venetian sumach (Rhus Cotinus) is both astringent and aromatic. It was at one time employed as a substitute for cinchona. Under the name of Smoke tree it is frequently observed in cultivation for ornament in American yards and gardens. The wood of this species is known as young fustic and is much used in Greece to impart a beautiful yellow hue to woolen fabrics. In Italy, where it is known as scotino, the whole plant is used for tanning leather. Doctor's gum or Gum hog of Jamaica, is one of the substances once considerably used as a plaster-base, and substituted, in some instances, for copaiba balsam. It has been referred to Rhus Metopium, though as is often the case, the same common names have been applied to the products of widely different species, therefore there seems to be no certain evidence that the species of Rhus referred to produces it. Doctor's gum, when dissolved in water, is powerfully cathartic and emetic, and was formerly in great repute as a diuretic. The most poisonous species of Rhus is the recently rediscovered Rhus Michauxii, Sargent(Rhus pumila, Michaux). Occupying a second place in toxic power is the Rhus venenata, well known as Poison dogwood, Poison sumach, or Poison elder. The Rhus vernix of Japan yields a whitish resinous varnish in small amount, which turns black on exposure to air. An oil, known as Japanese wax, is expressed from the seeds of Rhus succedaneum, which is employed by the Japanese in the making of candles to be used in times of special pagan festivities and in preparing certain kinds of food (Thunberg). A like oil is obtained from the fruit of the Lacquer tree. The Japan varnish or Lacquer tree is the Rhus vernicifera of De Candolle. From this plant exudes the gum-resinous substance used in making the celebrated Japanese lacquer-work. At first this juice is of a light color, and about as thick as cream. It is, however, so transparent that when laid unmixed with any other material upon wood even the faintest natural marking of the wood is plainly discernible through it. Generally a dark or reddish surface is first prepared and upon it the varnish is spread. This gives a mirror-like effect. The gum, when hardened, is difficultly soluble, even withstanding treatment with boiling water, but on the other hand is so brittle as to be very easily destroyed by striking it against any hard body. The Rhus Coriaria is powerfully astringent, and is much employed in tanneries. According to Lindley, its acid fruit is eaten by the Turks, who also employ it to add sharpness to vinegar. In Tripoli the seeds are sold as appetizers. The leaves are reputed astringent, tonic, cooling, and styptic, and boiled with broom (Genista tinctoria) were formerly employed by the Russians in hydrophobia. Smooth sumach (Rhus glabra) leaves are sufficiently astringent to be of importance in an economic sense, as in tanning. The fruit is employed as a mordant in dyeing red. The under surfaces of smooth sumach leaves produce excrescences which contain an abundance of tannic and gallic acids, and are considered equal in value to common galls. Staghorn or Virginian sumach (Rhus typhina) is sometimes called Vinegar plant from the fact that vinegar may be produced from it, and that when added to vinegar it increases its strength. Boiled with alum, the ripe fruit formerly furnished a hat dye. Yellow, green and black are the colors that may be produced from it. With green vitriol it forms a black ink. All parts of the plant are valued for tanning white glove-leather. The milky juice is said to furnish a varnish comparing favorably in value with that from Japan. It has been stated that honey-bees gather more honey from its flowers, when accessible, than from those of any other species of plants. The leaves were used like tobacco by the American Indians.

Indigenous Species.—The medicinal species of Rhus indigenous to North America are distributed as follows:


  • Rhus glabra, Linné.—A smooth shrub, known as Smooth or Upland sumach, found throughout the United States and Canada, flourishing in dry, barren or rocky situations, fence corners, etc. (see Rhus glabra).
  • Rhus typhina, Linné, Staghorn or Virginian sumach.—A shrub or small tree of Canada an a the United States, growing in the rich soil of uplands.
  • Rhus copallina, Linné, Dwarf or Mountain sumach.—A small shrub found throughout Canada and the United States, growing in rocky and barren places.
  • Rhus aromatica, Aiton, Sweet or Fragrant sumach.—Eastern United States. A variety (R. aromatica var. trilobiata, Gray) is found in Texas and in the western states and territories (see Rhus aromatica).


  • Rhus Michauxii, Sargent (Rhus pumila, Michaux).—A rare shrub, recently rediscovered in North Carolina, regarded by Prof. C. S. Sargent as our most poisonous species of Rhus. Grows from North Carolina to Georgia (Wood).
  • Rhus venenata, De Candolle, Poison sumach, Poison dogwood, or Poison elder. Grows in swamps and other wet situations from Canada southward to Florida, and thence westward.
  • Rhus diversiloba, Torrey and Gray.—Closely allied to Rhus Toxicodendron, and growing on the Pacific coast.
  • Rhus Toxicodendron, Poison ivy, or Poison oak.—Either a small shrub or a tall climbing vine growing from 10 to 100 feet high, found plentifully from Canada to the Mexican Gulf and from thence westward. Dr. Asa Gray, in his essay on "Sequoia and Its History," says: "Our Rhus Toxicodendron, or Poison vine, is very exactly repeated in Japan, but is found in no other part of the world, although a species much like it abounds in California. Our other poisonous Rhus (R. venenata) commonly called Poison dogwood is in no way represented in western America, but has so close an analogue in Japan that the two were taken for the same by Thunberg and Linnaeus, who called them both Rhus vernix." This explains why our older writers on the American Rhus venenata called it R. vernix. The species often spoken of as Rhus radicans, from the fact that it is a tall climber clinging by means of its numerous radicles to any object of support, is probably identical with Rhus Toxicodendron, or Poison vine, and is so considered in this article.

Description.—FOLIA TOXICODENDRI. The U. S. P. thus describes the drug: "Long-petiolate, trifoliolate; the lateral leaflets sessile or nearly so, about 10 Cm. (4 inches) long, obliquely ovate, pointed; the terminal leaflets stalked, ovate or oval, pointed, with a wedge-shaped or rounded base; the leaflets entire and glabrous, or variously notched, coarsely toothed or lobed, more or less downy; when dry, papery and brittle; inodorous; taste somewhat astringent and acrid. The fresh leaves abound with an acrid juice, which darkens when exposed to the air, and, when applied to the skin, produces inflammation and swelling. The leaves should, therefore, not be touched with bare hands. Rhus Toxicodendron should not be confounded with the leaves of Ptelea trifoliata, Linné (Nat. Ord.—Rutaceae), which are similar in appearance, but have all the leaflets sessile"—(U. S. P.). The leaves of the R. Toxicodendron are the only parts of the plant used, although the whole plant is highly active. When dried they have no odor, and an insipid taste with acridity. Water or alcohol extracts their properties.

Chemical Composition.—Dr. Joseph Khittal (Wittstein's Vierteljahrsschrift, 1858, p. 348) found the leaves to contain chlorophyll, wax, resin, starch, tannin (rhus-tannic acid), etc., and a volatile alkaloid which exists in the plant combined with acids, and to which, he asserts, the toxic properties of the leaves are due. This opinion is contradicted, however, by Prof. Maisch. According to this authority, the exhalations of vigorous leaves redden blue litmus paper previously moistened, and contain volatile toxicodendric acid, the active principle. Its reactions do no coincide with those of formic acid (Amer. Jour. Pharm., 1866, p. 6). Dr. Pfaff and S. S. Orr, however, state this acid in pure condition to be non-toxic, and that the real active principle is a non-volatile oil, toxicodendrol, allied to cardol, from cashew-nut. The oil is soluble in alcohol and forms an insoluble lead compound. Thus the authors recommend the use of an alcoholic solution of lead acetate as a wash in cases of poisoning (Pharm. Jour. Trans., 1894-95, Vol. XXV, p. 818; also see V. K. Chesnut, in Yearbook U. S. Dept. Agr., 1896, p. 139). The efficiency of this antidote has long been known (see Maisch, loc. cit.); among other remedies suggested are ammonium chloride, washing soda, sodium hyposulphite, potassium permanganate, aqua ammoniae, or the bruised plant of Pilea pumila (Amer. Jour. Pharm., 1888, p. 390), fluid extract of serpentaria (ibid., 1884, p. 355), etc. Also compare interesting article, by G. M. Beringer, on Rhus poisoning (ibid., 1896, p. 18).

Early Medical History of the Species of Rhus.—Medical interest, in the species of Rhus, during the early history of this genus, seems to have centered chiefly in two species—R. Toxicodendron and R. glabra. Rhus venenata (as R. vernix), was quite fully considered, more however, with a view to studying its juice from an economic view, and its poisonous qualities and the remedies therefor. We are not aware that it has been medicinally employed, to any extent at least. Rhus glabra received a good share of attention from the profession and probably had its medicinal starting point from its aboriginal and domestic uses. One of the most interesting accounts of some species of Rhus is "An Experimental Dissertation on the Rhus vernix (venenata), Rhus radicans, and Rhus glabrum; commonly known in Pennsylvania by the names of Poison ash, Poison vine, and Common sumach, by Thomas Horsfield, of Bethlehem, Pa.," published in 1798. This interesting 88-page book gives a most excellent résumé of the knowledge of those species acquired up to that date, and we might add that the description of the effects of the poisonous species has not, in our opinion, been excelled to this day.

Rhus Toxicodendron is almost universally admitted to have been introduced to the profession, in 1793, by Dr. I. Alderson, of Hull, England, that gentleman first using it as a remedy in paralytic states. Dr. Du Fresnoy, of France, however, previous to this had employed Rhus radicans in paralytic and herpetic disorders. This was in 1788, and if we consider Rhus radicans and Rhus Toxicodendron as identical, this gives Du Fresnoy priority. It further seems that Gleditsch, in 1782, wrote an article (in French) on "Novel Effects Concerning a Dangerous American Plant," referring to Rhus. Du Fresnoy first experimented on himself before administering the leaves to his patient. His experience with an infusion of 12 leaves he thus records: "At this dose I observed a slight pain in my stomach, and my perspiration and urine were increased in quantity." Alderson observed that when the drug acted beneficially in paralysis, "the first signs of improvement were an unpleasant feeling of pricking and twitching in the paralytic limbs" (Thacher's Dispensatory, 1821). Du Fresnoy's dissertation was the first publication in regard to the medical uses of Rhus. Horsfield (1798) experimented on consumptives with the infusion. In some cases benefit seemed to be derived from its use, while other cases were aggravated by it. He states of the wife of a consumptive patient that, "invited by the agreeable odor of the infusion, she drank a teacupful. It produced an unusual degree of cheerfulness, and a copious discharge of urine" (Diss., p. 87). In a case of anasarca, it relieved the patient by "producing copious perspiration" (ibid). He concluded from his results that it "acts slightly as an incitant and diuretic." A tincture was used by Baudelocque in scrofulous chronic ophthalmia of infants (Porcher).

Rhus glabra was used early by American practitioners as an astringent in diarrhoea, dysentery, and in ulceration of the throat, etc. The fruit (sumach bobs) infused in water, was employed as a cooling drink in febrile affections. The whitish substance covering the berries, known as Indian salt, has acid properties, rendering the infusion pleasantly sour. Rhus copallina and Rhus typhina were used for like purposes, while the first was valued by the Chippewa Indians in gonorrhoea, and the gall-like excrescences on the leaves, powdered and made into an ointment, afforded the white settlers a remedy for piles (see Rhus Glabra).

Rhus diversiloba appears to have been effectual in dysmenorrhoea. A case (in California) is reported (Ec. Med. Jour., 1865, p. 314) of an anemic girl, who usually suffered greatly during menstruation, the flow being scanty, cured by having been poisoned at the menstrual epoch by contact with this plant. An easy menstruation followed. When the next monthly period was due a return of the eruption came also, and with it again an easy catamenial flow. This, so far as we are aware, is the extent to which this plant has been known to act medicinally, though nearly all old works state that its properties are similar to those of Rhus Toxicodendron, and Rhus venenata. The latter, we believe, has not been employed in medicine (see Related Species).

Rhus aromatica was introduced to the profession by an Eclectic physician, Dr. J. T. McClanahan, of Booneville, Mo., in 1879, who stated that the remedy had been employed by members of his family, several of whom were doctors, for a quarter of a century, for the relief of urinary, bowel, and hemorrhagic disorders, with uniform success (see Rhus Aromatica).

Cont'd on next page.

King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.