Scientific Name(s): Toxicodendron diversilobum (Torr. & A. Gray) Greene, Toxicodendron pubescens Mill., Toxicodendron radicans (L.) Kuntze, Toxicodendron rydbergii (Small ex Rydb.) Greene, Toxicodendron succedaneum (L.) Kuntze, Toxicodendron vernicifluum (Stokes) F.A. Barkley, Toxicodendron vernix (L.) Kuntze
Common Name(s): Chinese lacquer, Markweed, Poison dogwood, Poison elder, Poison ivy, Poison oak, Poison sumac
"Poison ivy" or "poison oak" refers to several members of the Toxicodendron genus (formerly Rhus), which grow throughout the United States. Identification of the exact species has traditionally relied on the adage "leaves of 3, let it be;" however, poison oak can have 3 to 5 leaflets and nonpoisonous sumac can have up to 13 leaflets. The nontoxic Virginia creeper (Parthenocissus quinquefolia) can also be mistaken for poison ivy.1, 2, 3
Images for identification are available on the US Department of Agriculture’s online PLANTS Database.1 Generally, all species have U- or V-shaped leaf scars (where the leaf breaks from the stem), and flowers and fruits arise in the axillary position (the angle between the leaf and the branch). A black deposit is often present when Toxicodendron has been injured. Following trauma, the toxic oleoresin exudes, darkens with exposure to air, and hardens, which may assist in identification.2 Synonyms of T. pubescens include Rhus acutiloba, Rhus toxicarium, Rhus toxicodendron, Toxicodendron quercifolium, and Toxicodendron toxicarium.
An oily phenolic resin, termed "lobinol" by James B. McNair of the University of Chicago in the 1920s,4 is present in all poisonous Toxicodendron species and contains urushiol, a complex active principle derived from the Japanese term "sap." Urushiol is a mixture of antigenic catechols closely related to 3-n-pentadecylcatechol (3- PDC, hydrourushiol), varying in degree of saturation and length of side chain,2, 5 and carried by resin canals in the bark, stem, leaflets, and certain flower parts. The relative percentages of 3-PDC and related catechols vary among the species and may be related to environmental conditions. The danger of toxicity is greatest in spring and summer when the sap is abundant, the urushiol content is high, and the plant is easily bruised.2 Other chemical compounds in poison ivy include fisetin, gallotannic acid, kaempferol, myricetin, quercetin, rhamnose, and tannins.5 Additionally, heneicosandicarbonic, myristic, and palmitic acids have been identified in the fruit, and linoleic and oleic acids in the seeds.5
The chemical composition of T. vernicifluum, and the lacquer sap/wax obtained from this species, is also under investigation, with polysaccharides, phenolic, and sesquiterpenoid compounds of interest.6, 7, 8, 9, 10
Uses and Pharmacology
Anti-inflammatory activity has been described in rodent studies using homeopathic R. toxicodendron.13, 14, 15, 16, 17, 18 However, analytical documentation of the content and strength of the preparations used was not included.
A multicenter, randomized trial (N = 142) evaluated the homeopathic preparation Disci/Rhus toxicodendron compositum (a composite medication authorized in Germany) in low back pain. The homeopathic injection preparation (51 patients) was not superior to placebo injections (48 patients), but did result in clinically relevant pain relief in comparison to no treatment (51 patients).19
Pregnancy / Lactation
Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented. A delayed hypersensitivity reaction (Rhus allergic contact dermatitis) occurred in a patient taking etanercept.21
Mild to severe allergic contact dermatitis, typically a pruritic, erythematous, and vesicular rash depending upon point of contact, is well documented. Black-spot poison ivy dermatitis has also been described, with characteristic black lesions.22, 23
Urushiol is degraded in water and immediate washing of the contact area with a detergent-containing or "grease-cutting" soap is advised.2 Findings from a randomized clinical study suggest that long courses (15 days, with tapering) of oral corticosteroid treatment are more beneficial than short courses (5 days).24 Contact dermatitis from homeopathic R. toxicodendron has been reported,25 as has dermatitis from ingestion of Rhus lacquer.26 The oleoresin urushiol appears to be allergenic only to humans and higher primates. Desensitization is not generally successful.2
Dose-dependent genotoxicity has been observed in bone marrow of mice exposed to an extract of T. pubescens (Atlantic poison oak).27
This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.
This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.
Copyright © 2018 Wolters Kluwer Health
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.