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Installment 15 of a series on case analysis

© Will Taylor, MD 2001 (bio)

Families of Remedies

Sections: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

Section 3

Rhus Research

Poison Ivy, Oak and Sumac

The several Rhus species in our materia medica were an interesting exercise in research, and required pooling information from several resources. On the Rhus tox / Rhus radicans question, "Rhus toxicodendron" and "Rhus radicans" are terms that have been used historically somewhat interchangeably to describe theses 3 separate North American species:

  • Eastern Poison Ivy (Toxicodendron radicans)
  • Atlantic Poison Oak (Toxicodendron pubescens)
  • Pacific Poison Oak (Toxicodendron diversilobum)

Some taxonomic schemes retain "Rhus" as the genus name for these species, but Toxicodendron is more widely accepted

To complicate matters further, Eastern Poison Ivy (Toxicodendron radicans) has two growth habits, as a sub shrub/groundcover and as a vine, dependent on environmental conditions; which has occasionally resulted in its description as two distinct species (see the discussion of this in Charles Millspaugh's, American Medicinal Plants).

It appears that our Rhus-t and Rhus-r both refer to the single specie Toxicodendron radicans (Eastern Poison Ivy), with Rhus-r referring specifically to the vining habit of this plant.

It is possible that some Atlantic Poison Oak crept into the later American toxicological reports here and there, but the European experience (Hahnemann's proving, etc.) was more certain to be purely Eastern Poison Ivy.

There are no native European Rhus species; Toxicodendron radicans (Eastern Poison Ivy) was introduced to Europe as an ornamental in the mid-1600s. Atlantic Poison Oak is not present in Pennsylvania, Ohio, or the New England States (having a more southern distribution), so would not have been widely available to the early homeopaths of North America.

Rhus - poison ivy and poison sumac

So, in summary for Rhus:

Rhus-t ("Rhus toxicodendron") = Rhus-r ("Rhus radicans") = Toxicodendron radicans = Eastern Poison Ivy.

Rhus-d ("Rhus diversiloba") = Toxicodendron diversilobum = Pacific Poison Oak.

Rhus-a ("Rhus aromatica") is a correct reference to the Lemon Sumac of Eastern North America.

Rhus-c ("Rhus cotinus") = Cotinus coggygria = Venetian Sumac, Smoketree of S. Europe and W. Asia.

Rhus-g ("Rhus glabra") is a correct reference to the Smooth Sumac of North America.

Rhus-l ("Rhus laurina") = Malosma laurina = the Laurel Sumac of Southern California.

Rhus-v ("Rhus venenata") = Rhus-ver ("Rhus vernix") = Toxicodendron vernix, the Poison Sumac of Eastern North America.

Some taxonomic schemes (those that do the same for radicans and pubescens) retain "Rhus" as the genus name for this specie. Toxicodendron, though, is more widely accepted for the clearly dermatotoxic members of this group.

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