The percentage of persons susceptible to poison ivy and poison oak

Studies on the Biological Activity of Rhus striata (‘Manzanillo’)

“…A similar observation was made by Spain, N ew ell and M eeker (18), who established that the percentage of persons affected by different concentrations of poison ivy and poison oak extracts varied in a definite mathematical manner. These findings make us believe that skin toxicity of Rhus plants could be statistically analyzed, as is the action of drugs and some physiological stimuli, by so extending the range of concentrations to be tested as to obtain a complete dose-response curve.…”

In vitro studies of poison oak immunity. I. In vitro reaction of human lymphocytes to urushiol.

“…2 is the response of a subject to HDC, PDC, and urushiol from either poison ivy or poison oak. Like the in vivo response of subjects exposed to either plant (8,9) Doses of RBC-uru above 4 x 106 ME/well produced a diminished blastogenesis response. To determine whether this diminished blastogenic response was a result of a direct toxic effect of the antigen on the responder cells, a series of experiments using lymphocyte mitogens was carried out.…”

“…Whereas urushiol derived from poison ivy is composed predominantly of compounds with C-15 side chains (5), poison oak urushiol contains more of the compounds with C-17 side chains (6,7). The di-and tri-olefins are the major components of both urushiols, and the two oils are highly cross reactive (8). In vivo studies in humans sensitized by accidental exposure have shown that the dienes and the trienes are far more antigenic than the saturated components of the urushiol mixture, 3-n-pentadecycatechol (PDC)' and 3-n-heptadecylcatechol (HDC), which are about one-tenth as active as the corresponding dienes (9).…”